In linguistics, a corpus (plural corpora) or text corpus is a large and structured set of texts (now usually electronically stored and processed). They are used to do statistical analysis, checking occurrences or validating linguistic rules on a specific universe.

A corpus may contain texts in a single language (monolingual corpus) or text data in multiple languages (multilingual corpus). Multilingual corpora that have been specially formatted for side-by-side comparison are called aligned parallel corpora.

In order to make the corpora more useful for doing linguistic research, they are often subjected to a process known as annotation. An example of annotating a corpus is part-of-speech tagging, or POS-tagging, in which information about each word's part of speech (verb, noun, adjective, etc.) is added to the corpus in the form of tags. Another example is indicating the lemma (base) form of each word. When the language of the corpus is not a working language of the researchers who use it, interlinear glossing is used to make the annotation bilingual.

Corpora are the main knowledge base in corpus linguistics. The analysis and processing of various types of corpora are also the subject of much work in computational linguistics, speech recognition and machine translation, where they are often used to create hidden Markov models for POS-tagging and other purposes. Corpora and frequency lists derived from them are useful for language teaching.

Archaeological corpora

Text corpora. are also used in the study of historical documents, for example in attempts to decipher ancient scripts, or in Biblical scholarship. Some archaeological corpora can be of such short duration that they provide a snapshot in time. One of the shortest corpora in time, may be the 15-30 year Amarna letters texts-(1350 BC). The corpus of an ancient city, (for example the "Kültepe Texts" of Turkey), may go through a series of corpora, determined by their find site dates.

Some notable text corpora

English language:

• American National Corpus
• Bank of English
• British National Corpus
• Corpus Juris Secundum
• Corpus of Contemporary American English (COCA) 360 million words, 1990-2007. Freely available online.
• Brown Corpus, forming part of the "Brown Family" of corpora, together with LOB, Frown and F-LOB.
• Oxford English Corpus
• Scottish Corpus of Texts & Speech

Other languages:

• Amarna letters, (for Akkadian, Egyptian, Sumerogram's, etc.)
• Bijankhan Corpus A Contemporary Persian Corpus for NLP researches
• Croatian National Corpus
• Hamshahri Corpus A Contemporary Persian Corpus for IR researches
• Neo-Assyrian Text Corpus Project
• Persian Today Corpus
• Thesaurus Linguae Graecae (Ancient Greek)

See also

• Concordance
• Corpus linguistics
• Linguistic Data Consortium
• Natural language processing
• Natural Language Toolkit
• Parallel text alignment
• Search engines: they access the "web corpus".
• Translation memory
• Treebank
• Zipf's Law

External links

• Freely-available, web-based corpora (100 million - 360 million words each): American, British (BNC), TIME, Spanish, Portuguese
• ACL SIGLEX Resource Links: Text Corpora
• The Leipzig Glossing Rules: Conventions for interlinear morpheme-by-morpheme glosses
• Developing Linguistic Corpora: a Guide to Good Practice

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