A word list is a list of words in a lexicon, generally sorted by frequency of occurrence (either by graded levels, or as a ranked list). A word list is compiled by lexical frequency analysis within a given text corpus, and is used in corpus linguistics to investigate genealogies and evolution of languages and texts. A word which appears only once in the corpus is called a hapax legomena. In pedagogy, word lists are used in curriculum design for vocabulary acquisition. A lexicon sorted by frequency "provides a rational basis for making sure that learners get the best return for their vocabulary learning effort" (Nation 1997), but is mainly intended for course writers, not directly for learners. Frequency lists are also made for lexicographical purposes, serving as a sort of checklist to ensure that common words are not left out. Some major pitfalls are the corpus content, the corpus register, and the definition of "word". While word counting is a thousand years old, with still gigantic analysis done by hand in the mid-20th century, natural language electronic processing of large corpora such as movie subtitles (SUBTLEX megastudy) has accelerated the research field. In computational linguistics, a frequency list is a sorted list of words (word types) together with their frequency, where frequency here usually means the number of occurrences in a given corpus, from which the rank can be derived as the position in the list.
Methodology
Factors Nation (Nation 1997) noted the incredible help provided by computing capabilities, making corpus analysis much easier. He cited several key issues which influence the construction of frequency lists:
corpus representativeness word frequency and range treatment of word families treatment of idioms and fixed expressions range of information various other criteria
Corpora
Traditional written corpus Most of currently available studies are based on written text corpus, more easily available and easy to process.
SUBTLEX movement However, New et al. 2007 proposed to tap into the large number of subtitles available online to analyse large numbers of speeches. Brysbaert & New 2009 made a long critical evaluation of the traditional textual analysis approach, and support a move toward speech analysis and analysis of film subtitles available online. The initial research saw a handful of follow-up studies, providing valuable frequency count analysis for various languages. In depth SUBTLEX researches over cleaned up open subtitles were produced for French (New et al. 2007), American English (Brysbaert & New 2009; Brysbaert, New & Keuleers 2012), Dutch (Keuleers & New 2010), Chinese (Cai & Brysbaert 2010), Spanish (Cuetos et al. 2011), Greek (Dimitropoulou et al. 2010), Vietnamese (Pham, Bolger & Baayen 2011), German (Brysbaert et al. 2011), Brazil Portuguese (Tang 2012) and Portugal Portuguese (Soares et al. 2015), Albanian (Avdyli & Cuetos 2013), Polish (Mandera et al. 2014) and Catalan (2019), Welsh (Van Veuhen et al. 2024), Korean. SUBTLEX-IT (2015) provides raw data only.
Lexical unit In any case, the basic "word" unit should be defined. For Latin scripts, words are usually one or several characters separated either by spaces or punctuation. But exceptions can arise : English "can't" and French "aujourd'hui" include punctuations while French "chateau d'eau" designs a concept different from the simple addition of its components while including a space. It may also be preferable to group words of a word family under the representation of its base word. Thus, possible, impossible, possibility are words of the same word family, represented by the base word *possib*. For statistical purpose, all these words are summed up under the base word form *possib*, allowing the ranking of a concept and form occurrence. Moreover, other languages may present specific difficulties. Such is the case of Chinese, which does not use spaces between words, and where a specified chain of several characters can be interpreted as either a phrase of unique-character words, or as a multi-character word.
Statistics It seems that Zipf's law holds for frequency lists drawn from longer texts of any natural language. Frequency lists are a useful tool when building an electronic dictionary, which is a prerequisite for a wide range of applications in computational linguistics. German linguists define the Häufigkeitsklasse (frequency class) N {\displaystyle N} of an item in the list using the base 2 logarithm of the ratio between its frequency and the frequency of the most frequent item. The most common item belongs to frequency class 0 (zero) and any item that is approximately half as frequent belongs in class 1. In the example list above, the misspelled word outragious has a ratio of 76/3789654 and belongs in class 16.
N = ⌊ 0.5 − log 2 ( Frequency of this item Frequency of most common item ) ⌋ {\displaystyle N=\left\lfloor 0.5-\log _{2}\left({\frac {\text{Frequency of this item}}{\text{Frequency of most common item}}}\right)\right\rfloor }
where ⌊ … ⌋ {\displaystyle \lfloor \ldots \rfloor } is the floor function. Frequency lists, together with semantic networks, are used to identify the least common, specialized terms to be replaced by their hypernyms in a process of semantic compression.
Pedagogy Those lists are not intended to be given directly to students, but rather to serve as a guideline for teachers and textbook authors (Nation 1997). Paul Nation's modern language teaching summary encourages first to "move from high frequency vocabulary and special purposes [thematic] vocabulary to low frequency vocabulary, then to teach learners strategies to sustain autonomous vocabulary expansion" (Nation 2006).
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