Proceedings of the Fifth SIGHAN Workshop on Chinese Language Processing, pages 17–24,
Sydney, July 2006. c©2006 Association for Computational Linguistics
Mining Atomic Chinese Abbreviation Pairs: A Probabilistic Model for
Single Character Word Recovery
Jing-Shin Chang
Department of Computer Science &
Information Engineering
National Chi-Nan University
Puli, Nantou, Taiwan, ROC.
jshin@csie.ncnu.edu.tw
Wei-Lun Teng
Department of Computer Science &
Information Engineering
National Chi-Nan University
Puli, Nantou, Taiwan, ROC.
S3321512@ncnu.edu.tw
Abstract
An HMM-based Single Character
Recovery (SCR) Model is proposed in
this paper to extract a large set of
“atomic abbreviation pairs”from a large
text corpus. By an“atomic abbreviation
pair,”it refers to an abbreviated word
and its root word (i.e., unabbreviated
form) in which the abbreviation is a
single Chinese character.
This task is interesting since the
abbreviation process for Chinese
compound words seems to be
“compositional”; in other words, one
can often decode an abbreviated word,
such as“台大”(Taiwan University),
character-by-character back to its root
form. With a large atomic abbreviation
dictionary, one may be able to recover
multiple-character abbreviations more
easily.
With only a few training iterations, the
acquisition accuracy of the proposed
SCR model achieves 62% and 50 %
precision for training set and test set,
respectively, from the ASWSC-2001
corpus.
1 Introduction
Chinese abbreviations are widely used in the
modern Chinese texts. They are a special form
of unknown words, which cannot be
exhaustively enumerated in an ordinary
dictionary. Many of them originated from
important lexical units such as named entities.
However, the sources for Chinese abbreviations
are not solely from the noun class, but from most
major categories, including verbs, adjectives
adverbs and others. No matter what lexical or
syntactic structure a string of characters could be,
one can almost always find a way to abbreviate
it into a shorter form. Therefore, it may be
necessary to handle them beyond a class-based
model. Furthermore, abbreviated words are
semantically ambiguous. For example,“清大”
can be the abbreviation for“清華大學”or“清潔
大 隊”; on the opposite direction, multiple
choices for abbreviating a word are also possible.
For instance,“台北大學”may be abbreviated as
“台大”,“北大”or“台北大”. This results in
difficulty for correct Chinese processing and
applications, including word segmentation,
information retrieval, query expansion, lexical
translation and much more. An abbreviation
model or a large abbreviation lexicon is
therefore highly desirable for Chinese language
processing.
Since the smallest possible Chinese lexical
unit into which other words can be abbreviated
is a single character, identifying the set of
multi-character words which can be abbreviated
into a single character is especially interesting.
Actually, the abbreviation of a compound word
can often be acquired by the principle of
composition. In other words, one can decompose
a compound word into its constituents and then
concatenate their single character equivalents to
form its abbreviated form. The reverse process
to predict the unabbreviated form from an
abbreviation shares the same compositional
property.
The Chinese abbreviation problem can be
regarded as an error recovery problem in which
the suspect root words are the “errors” to be 
recovered from a set of candidates. Such a
problem can be mapped to an HMM-based
generation model for both abbreviation
identification and root word recovery; it can also
17
be integrated as part of a unified word
segmentation model when the input extends to a
complete sentence. As such, we can find the
most likely root words, by finding those
candidates that maximizes the likelihood of the
whole text. An abbreviation lexicon, which
consists of the root-abbreviation pairs, can thus
be constructed automatically.
In a preliminary study (Chang and Lai, 2004),
some probabilistic models had been developed
to handle this problem by applying the models to
a parallel corpus of compound words and their
abbreviations, without knowing the context of
the abbreviation pairs. In this work, the same
framework is extended and a method is proposed
to automatically acquire a large abbreviation
lexicon for indivisual characters from web texts
or large corpora, instead of building abbreviation
models based on aligned abbreviation pairs of
short compound words. Unlike the previous task,
which trains the abbreviation model parameters
from a list of known abbreviation pairs, the
current work aims at extracting abbreviation
pairs from a corpus of free text, in which the
locations of prospective abbreviations and full
forms are unknown and the correspondence
between them is not known either.
In particular, a Single Character Recovery
(SCR) Model is exploited in the current work to
extract“atomic abbreviation pairs”from a large
text corpus. With only a few training iterations,
the acquisition accuracy achieves 62% and 50 %
precision for training set and test set from the
ASWSC-2001 corpus.
1.1 Chinese Abbreviation Problems
The modern Chinese language is a highly
abbreviated one due to the mixed uses of ancient
single character words as well as modern
multi-character words and compound words.
The abbreviated form and root form are used
interchangeably everywhere in the current
Chinese articles. Some news articles may
contain as high as 20% of sentences that have
suspect abbreviated words in them (Lai, 2003).
Since abbreviations cannot be enumerated in a
dictionary, it forms a special class of unknown
words, many of which originate from named
entities. Many other open class words are also
abbreviatable. This particular class thus
introduces complication for Chinese language
processing, including the fundamental word
segmentation process (Chiang et al., 1992; Lin
et al., 1993; Chang and Su, 1997) and many
word-based applications. For instance, a
keyword-based information retrieval system may
requires the two forms, such as“中研院”and
“中央研究院”(“Academia Sinica”), in order not
to miss any relevant documents. The Chinese
word segmentation process is also significantly
degraded by the existence of unknown words
(Chiang et al., 1992), including unknown
abbreviations.
There are some heuristics for Chinese
abbreviations. Such heuristics, however, can
easily break (Sproat, 2002). Unlike English
abbreviations, the abbreviation process of the
Chinese language is a very special word
formation process. Almost all characters in all
positions of a word can be omitted when used
for forming an abbreviation of a compound word.
For instance, it seems that, by common
heuristics,“most”Chinese abbreviations could
be derived by keeping the first characters of the
constituent words of a compound word, such as
transforming‘台 灣 大 學’into‘台大’,‘清 華 大
學’into‘清大’and‘以 色列 ( 及 ) 巴 勒斯坦’into
‘以巴’. Unfortunately, it is not always the case.
For example, we can transform‘台 灣香 港’into
‘台港’,‘中 國石 油’into‘中油’, and, for very
long compounds like‘雲 林 嘉 義台 南’into‘雲
嘉南’(Sproat, 2002). Therefore, it is very
difficult to predict the possible surface forms of
Chinese abbreviations and to guess their base
(non-abbreviated) forms heuristically.
P(bit|n) Score Examples
P(10|2) 0.87 (德 |德國 ),(美 |美國 )
P(101|3) 0.44 (宜縣 |宜蘭縣 ),
(限級 |限制級 )
P(1010|4) 0.56 (公投 |公民投票 ),
(清大 |清華大學 )
P(10101|5) 0.66 (環保署 |環境保護署 ),
(航警局 |航空警察局 )
P(101001|6) 0.51 (化工系 |化學工程學系 ),
(工工系 |工業工程學系 )
P(1010001|7) 0.55 (國科會 |國家科學委員會 ),
(中科院 |中山科學研究院 )
P(10101010|8) 0.21 (一中一台 |一個中國一個台
灣 ),
( 一大一小 |一個大人一個小
孩 )
Table 1. High Frequency Abbreviation Patterns
[by P(bit|n)] (Chang and Lai, 2004)
18
The high frequency abbreviation patterns
revealed in (Chang and Lai, 2004) further break
the heuristics quantitatively. Table 1 lists the
distribution of the most frequent abbreviation
patterns for word of length 2~8 characters.
The table indicates which characters will be
deleted from the root of a particular length (n)
with a bit ‘0’; on the other hand, a bit ‘1’ means
that the respective character will be retained.
This table does support some general heuristics
for native Chinese speaker quantitatively. For
instance, there are strong supports that the first
character in a two-character word will be
retained in most cases, and the first and the third
characters in a 4-character word will be retained
in 56% of the cases. However, the table also
shows that around 50% of the cases cannot be
uniquely determined by character position
simply by consulting the word length of the
un-abbreviated form. This does suggest the
necessity of either an abbreviation model or a
large abbreviation lexicon for resolving this kind
of unknown words and named entities.
There are also a large percentage (312/1547)
of “tough” abbreviation patterns (Changand Lai,
2004), which are considered “tough”in the sense
that they violate some simple assumptions, and
thus cannot be modeled in a simple way. For
instance, some tough words will actually be
recursively abbreviated into shorter and shorter
lexical forms; and others may change the word
order (as in abbreviating“第 一核 能發電廠”as
“核一 廠”instead of“一核 廠”.). As a result, the
abbreviation process is much more complicated
than a native Chinese speaker might think.
1.2 Atomic Abbreviation Pairs
Since the abbreviated words are created
continuously through the abbreviation of new
(mostly compound) words, it is nearly
impossible to construct a complete abbreviation
lexicon. In spite of the difficulty, it is interesting
to note that the abbreviation process for Chinese
compound words seems to be“compositional”.
In other words, one can often decode an
abbreviated word, such as“台大”(“Taiwan
University”), character-by-character back to its
root form“台灣大學”by observing that“台”
can be an abbreviation of“台灣”and“大”can
be an abbreviation of“大學”and“台灣大學”is
a frequently observed character sequence.
Since character is the smallest lexical unit for
Chinese, no further abbreviation into smaller
units is possible. We therefore use“atomic
abbreviation pair”to refer to an abbreviated
word and its root word (i.e., unabbreviated form)
in which the abbreviation is a single Chinese
character.
On the other hand, abbreviations of
multi-character compound words may be
synthesized from single characters in the
“atomic abbreviation pairs”. If we are able to
identify all such“atomic abbreviation pairs”,
where the abbreviation is a single character, and
construct such an atomic abbreviation lexicon,
then resolving multiple character abbreviation
problems, either by heuristics or by other
abbreviation models, might become easier.
Furthermore, many ancient Chinese articles
are composed mostly of single-character words.
Depending on the percentage of such
single-character words in a modern Chinese
article, the article will resemble to an ancient
Chinese article in proportional to such a
percentage. As another application, an effective
single character recovery model may therefore
be transferred into an auxiliary translation
system from ancient Chinese articles into their
modern versions. This is, of course, an overly
bold claim since lexical translation is not the
only factor for such an application. However, it
may be consider as a possible direction for
lexical translation when constructing an
ancient-to-modern article translation system.
Also, when a model for recovering atomic
translation pair is applied to the“single character
regions”of a word segmented corpus, it is likely
to recover unknown abbreviated words that are
previously word-segmented incorrectly into
individual characters.
An HMM-based Single Character Recovery
(SCR) Model is therefore proposed in this paper
to extract a large set of“atomic abbreviation
pairs”from a large text corpus.
1.3 Previous Works
Currently, only a few quantitative approaches
(Huang et al., 1994a; Huang et al., 1994b) are
available in predicting the presence of an
abbreviation. There are essentially no prior arts
for automatically extracting atomic abbreviation
pairs. Since such formulations regard the word
segmentation process and abbreviation
19
identification as two independent processes, they
probably cannot optimize the identification
process jointly with the word segmentation
process, and thus may lose some useful
contextual information. Some class-based
segmentation models (Sun et al., 2002; Gao et
al., 2003) well integrate the identification of
some regular non-lexicalized units (such as
named entities). However, the abbreviation
process can be applied to almost all word forms
(or classes of words). Therefore, this particular
word formation process may have to be handled
as a separate layer in the segmentation process.
To resolve the Chinese abbreviation
problems and integrate its identification into the
word segmentation process, (Chang and Lai,
2004) proposes to regard the abbreviation
problem in the word segmentation process as an
“error recovery” problem in which the suspect 
root words are the “errors” to be recovered from 
a set of candidates according to some generation
probability criteria. This idea implies that an
HMM-based model for identifying Chinese
abbreviations could be effective in either
identifying the existence of an abbreviation or
the recovery of the root words from an
abbreviation.
Since the parameters of an HMM-like model
can usually be trained in an unsupervised
manner, and the “output probabilities” known to 
the HMM framework will indicate the likelihood
for an abbreviation to be generated from a root
candidate, such a formulation can easily be
adapted to collect highly probable
root-abbreviation pairs. As a side effect of using
HMM-based formulation, we expect that a large
abbreviation dictionary could be derived
automatically from a large corpus or from web
documents through the training process of the
unified word segmentation model.
In this work, we therefore explore the
possibility of using the theories in (Chang and
Lai, 2004) as a framework for constructing a
large abbreviation lexicon consisting of all
Chinese characters and their potential roots. In
the following section, the HMM models as
outlined in (Chang and Lai, 2004) is reviewed
first. We then described how to use this
framework to construct an abbreviation lexicon
automatically. In particular, a Single Character
Recovery (SCR) Model is exploited for
extracting possible root (un-abbreviated) forms
for all Chinese characters.
2 Chinese Abbreviation Models
2.1 Unified Word Segmentation Model for
Abbreviation Recovery
To resolve the abbreviation recovery problem,
one can identify some root candidates for
suspect abbreviations (probably from a large
abbreviation dictionary if available or from an
ordinary dictionary with some educated guesses),
and then confirm the most probable root by
consulting local context. This process is
identical to the operation of many error
correction models, which generate the candidate
corrections according to a reversed word
formation process, then justify the best
candidate.
Such an analogy indicates that we may use an
HMM model (Rabiner and Juang, 1993), which
is good at finding the best unseen state sequence,
for root word recovery. There will be a direct
map between the two paradigms if we regard the
observed input character sequence as our
“observation sequence”, and regard the unseen 
word candidates as the underlying “state 
sequence”.
To integrate the abbreviation process into the
word segmentation model, firstly we can regard
the segmentation model as finding the best
underlying words mm www ,,11(which
include only base/root forms), given the surface
string of characters nn ccc ,,11(which may
contain abbreviated forms of compound words.)
The segmentation process is then equivalent to
finding the best (un-abbreviated) word
sequence *wsuch that:











ii
nmm
nmm
nmm
cw
mi
iiii
cww
mmn
cww
nm
cww
wwPwcP
wPwcP
cwPw



,1
1
:
111
:
11
:
||maxarg
|maxarg
|maxarg*
111
111
111
Equation 1. Unified Word Segmentation
Model for Abbreviation Recovery
20
where icrefers to the surface form of iw ,
which could be in an abbreviated or
non-abbreviated root form of iw . The last
equality assumes that the generation of an
abbreviation is independent of context, and the
language model is a word-based bigram model.
If no abbreviated words appears in real text,
such that all surface forms are identical to their
“root” forms, we will have| 1i iP c w,
1,i m, and Equation 1 is simply a word
bigram model for word segmentation (Chiang et
al., 1992). In the presence of abbreviations,
however, the generation probabilityii wcP |
can no longer be ignored, since the probability
ii wcP |is not always 1 or 0.
As an example, if two consecutive icare
‘台’and‘大’then their roots, iw , could be‘台
灣’plus‘大 學’ (Taiwan University) or‘台 灣’
plus‘大 聯盟’ (Taiwan Major League). In this 
case, the parameters in P(大學 |台灣 ) x P(台 |台
灣 ) x P(大 |大 學 ) and P(大聯盟 |台灣 ) x P(台 |台
灣 ) x P(大 |大 聯盟) will indicate how likely ‘台
大’ is an abbreviation, and which of the above 
two compounds is the root form.
Notice that, this equation is equivalent to an
HMM (Hidden Markov Model) (Rabiner and
Juang, 1993) normally used to find the best
“state” sequence given the observation symbols. 
The parameters1|ii wwP andii wcP |
represent the transition probability and the
(word-wise) output probability of an HMM,
respectively; and, the formulations formwP 1
andmn wcP 11 | are the respective“language 
model” of the Chinese language and the
“generation model” for the abbreviated words
(i.e., the“abbreviation model”in the current
context). The “state” sequence in this case is
characterized by the hidden root forms
m
m www ,,
11; and, the “observation 
symbols” are characterized by
mn
n ccccc,,,,
111, where the surface
formie ibi ccis a chunk of characters
beginning at the b(i)-th character and ending at
the e(i)-th character.
The word-wise transition probability
1|ii wwP in the language model is used to
provide contextual constraints among root words
so that the underlying word sequence forms a
legal sentence with high probability.
Notice that, after applying the word
segmentation model Equation 1 to the word
lattice, some of the above candidates may be
preferred and others be discarded, by consulting
the neighboring words and their transition
probabilities. This makes the abbreviation model
jointly optimized in the word segmentation
process, instead of being optimized independent
of context.
2.2 Simplified Abbreviation Models
Sometimes, it is not desirable to use a
generation probability that is based on the
root-abbreviation pairs, since the number of
parameters will be huge and estimation error due
to data sparseness might be high. Therefore, it is
desirable to simplify the abbreviation probability
by using some simpler features in the model. For
instance, many 4-character compound words are
abbreviated as 2-character abbreviations (such as
in the case for the <台灣大學,台大> pair.) It
was also known that many such 4-character
words are abbreviated by preserving the first and
the third characters, which can be represented by
a ‘1010’ bit pattern, where the ‘1’ or‘0’means
to preserve or delete the respective character.
Therefore, a reasonable simplification for the
abbreviation model is to introduce the length and
the positional bit pattern as additional features,
resulting in the following augmented model for
the abbreviation probability.
1 1
1 1
| ( , , | , )
( | ) ( | ) ( | )
m n
m n
P c w P c bit m r n
P c r P bit n P m n



1
1
: surface characters.
: root word characters.
where : length of surface characters.
: length of root word characters.
bit: bit pattern of abbreviation
m
n
c
r
m
n







Equation 2. Abbreviation Probability using
Abbreviation Pattern and Length Features.
All these three terms can be combined freely
to produce as many as 7 sub-models for the
21
abbreviation model. Note, the first term
nm rc
11 |Pr plays the same role as the older
notation ofwc |Pr. To use the simple length
and position features, this term can be unused in
the above augmented abbreviation model.
3 The Single Character Recovery (SCR)
Model
As mentioned earlier, many multiple
character words are frequently abbreviated into a
single Chinese character. Compound words
consisting of a couple of such multiple character
words are then abbreviated by concatenating all
the single character abbreviations. This means
that those N-to-1 abbreviation patterns may form
the basis for the underlying Chinese abbreviation
process. The other M-to-N abbreviation patterns
might simply be a composition of such basic
N-to-1 abbreviations. The N-to-1 abbreviation
patterns can thus be regarded as the atomic
abbreviation pairs.
Therefore, it is interesting to apply the
abbreviation recovery model to acquire all basic
N-to-1 abbreviation patterns, in the first place,
so that abbreviations of multi-character words
can be detected and predicted more easily.
Such a task can be highly simplified if each
character in a text corpus is regarded as an
abbreviated word whose root form is to be
recovered. In other words, the surface form ic
in Equation 1 is reduced to a single character.
The abbreviation recovery model based on this
assumption will be referred to as the SCR
Model.
The root candidates for each single character
will form a word lattice, and each path of the
lattice will represent a non-abbreviated word
sequence. The underlying word sequence that is
most likely to produce the input character
sequence will then be identified as the best word
sequence. Once the best word sequence is
identified, the model parameters can be
re-estimated. And the best word sequence is
identified again. Such process is repeated until
the best sequence no more changes. In addition,
the corresponding <root, abbreviation> pairs will
be extracted as atomic abbreviation pairs, where
all the abbreviations are one character in size.
While it is overly simplified to use this SCR
model for conducting a general abbreviation
enhanced word segmentation process (since not
all single characters are abbreviated words), the
single character assumption might still be useful
for extracting roots of real single-character
abbreviations. The reason is that one only care to
use the contextual constraints around a true
single character abbreviation for matching its
root form against the local context in order to
confirm that the suspect root did conform to its
neighbors (with a high language model score).
An alternative to use a two-stage recovery
strategy, where the first stage applies a baseline
word segmentation model to identify most
normal words and a second stage to identify and
recover incorrectly segmented single characters,
is currently under investigation with other modes
of operations. For the present, the SCR model is
tested first as a baseline.
The HMM-based recovery models enables us
to estimate the model parameters using an
unsupervised training method that is directly
ported from the Baum-Welch re-estimation
formula (Rabiner and Juang, 1993) or a generic
EM algorithm (Dempster et al., 1977). Upon
convergence, we should be able to acquire a
large corpus of atomic abbreviation pairs from
the text corpus.
If a word-segmented corpus is available, we
can also use such re-estimation methods for
HMM parameter training in an unsupervised
manner, but with initial word transition
probabilities estimated in a supervised manner
from the seed.
The initial candidate <root, abbreviation>
pairs are generated by assuming that all
word-segmented words in the training corpus are
potential roots for each of its single-character
constituents. For example, if we have“台灣”
and“大學”as two word-segmented tokens, then
the abbreviation pairs <台 , 台灣 >, <灣 , 台灣 >,
<大 , 大學 > and <學 , 大學 > will be generated.
Furthermore, each single character by default is
its own abbreviation.
To estimate the abbreviation probabilities,
each abbreviation pair is associated with a
frequency count of the root in the word
segmentation corpus. This means that each
single-character abbreviation candidate is
22
equally weighted. The equal weighting strategy
may not be absolutely true (Chang and Lai,
2004). In fact, the character position and word
length features may be helpful as mentioned in
Equation 2. The initial probabilities are
therefore weighted differently according to the
position of the character and the length of the
root. The weighting factors are directly acquired
from a previous work in (Chang and Lai, 2004).
Before the initial probabilities are estimated,
Good-Turning smoothing (Katz, 1987) is applied
to the raw frequency counts of the abbreviation
pairs.
4 Experiments
To evaluate the SCR Model, the Academia
Sinica Word Segmentation Corpus (dated July,
2001), ASWSC-2001 (CKIP, 2001), is adopted
for parameter estimation and performance
evaluation. Among the 94 files in this balanced
corpus, 83 of them (13,086KB) are randomly
selected as the training set and 11 of them
(162KB) are used as the test set.
Table 3 shows some examples of atomic
abbreviation pairs acquired from the training
corpus. The examples here partially justify the
possibility to use the SCR model for acquiring
atomic abbreviation pairs from a large corpus.
The iterative training process converges
quickly after 3~4 iterations. The numbers of
unique abbreviation patterns for the training and
test sets are 20,250 and 3,513, respectively.
Since the numbers of patterns are large, a rough
estimate on the acquisition accuracy rates is
conducted by randomly sampling 100 samples of
the <root, abbreviation> pairs. The pattern is
then manually examined to see if the root is
correctly recovered. The precision is estimated
as 50% accuracy for the test set, and 62% for the
training set on convergence. Although a larger
sample may be necessary to get a better estimate,
the preliminary result is encouraging. Figures
1~4 demonstrate the curve of convergence for
the iterative training process in terms of pattern
number and accuracy.
SCR Model Training Set 擷取 pattern 數量
20307
20252 20250 20250
20220
20240
20260
20280
20300
20320
1 2 3 4
遞迴次數
Figure 1. Numbers of abbreviation patterns in
each iteration. (Training Set)
SCR Model Training Set 正確率
29%
45%
62% 62%
0%
20%
40%
60%
80%
1 2 3 4
遞迴次數
Figure 2. Acquisition accuracy for each iteration.
(Training Set)
SCR Model Test Set 擷取 pattern 數量
3521
3518
3515
3513
3512
3513
3514
3515
3516
3517
3518
3519
3520
3521
3522
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5
遞迴次數
Figure 3. Numbers of abbreviation patterns in
each iteration. (Test Set)
Abbr : Root Example Abbr : Root Example
籃 :籃球 籃賽 宣 :宣傳 文宣
檢 :檢查 安 檢 農 :農業 農牧
媒 :媒體 政媒 艙 :座艙 艙壓
宿 :宿舍 男舍 攜 :攜帶 攜械
臺 :臺灣 臺幣 汽 :汽車 汽機車
漫 :漫畫 動漫 咖 :咖啡店 網 咖
港 :香港 港人 職 :職業 現職
網 :網路 網咖 設 :設計 工 設 系
股 :股票 股市 湖 :澎湖 臺澎
韓 :韓國 韓流 海 :海洋 海生館
祕 :祕書 主秘 文 :文化 文 建會
植 :植物 植被 生 :學生 新生
儒 :儒家 新儒 學 新 :新加坡 新國
盜 :強盜 盜匪 花 :花蓮 花東
房 :房間 機 房 資 :資訊 資工
Table 3. Examples of atomic abbreviation pairs.
23
SCR Model Test Set 正確率
20% 22%
33%
50%
0%
10%
20%
30%
40%
50%
60%
1 2 3 4
遞迴次數
Figure 4. Acquisition accuracy for each iteration.
(Test Set)
5 Concluding Remarks
Chinese abbreviations, which form a special
kind of unknown words, are widely seen in the
modern Chinese texts. This results in difficulty
for correct Chinese processing. In this work, we
had applied a unified word segmentation model
developed in a previous works (Chang and Lai,
2004), which was able to handle the kind of
“errors” introduced by the abbreviation process. 
An iterative training process is developed to
automatically acquire an abbreviation dictionary
for single-character abbreviations from large
corpora. In particular, a Single Character
Recovery (SCR) Model is exploited. With only a
few training iterations, the acquisition accuracy
achieves 62% and 50 % precision for training set
and test set from the ASWSC-2001 corpus. For
systems that choose to lexicalize such lexicon
entities, the automatically constructed
abbreviation dictionary will be an invaluable
resource to the systems. And, the proposed
recovery model looks encouraging.

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