Corpus linguistics

Corpus linguistics is the study of language as expressed in samples (corpora) or "real world" text. This method represents a digestive approach to deriving a set of abstract rules by which a natural language is governed or else relates to another language. Originally done by hand, corpora are largely derived by an automated process, which is corrected. The core of a corpus is the derivation of a set of Part-of-speech tags, representing a formal overview of the various types of words and word-relationships in a given language.

Computational methods had once been viewed as a holy grail of linguistic research, which would ultimately manifest a ruleset for natural language processing and machine translation at a high level. Such has not been the case, and since the cognitive revolution, cognitive linguistics has been largely critical of many claimed practical uses for corpora. However, as computation capacity and speed have increased, the use of corpora to study language and term relationships en masse has gained some respectability.

The corpus approach runs counter to Noam Chomsky's view that real language is riddled with performance-related errors, thus requiring careful analysis of small speech samples obtained in a highly controlled laboratory setting. Corpus linguistics does away with Chomsky's competence/performance split; adherents believe that reliable language analysis best occurs on field-collected samples, in natural contexts and with minimal experimental interference.

History
A landmark in modern corpus linguistics was the publication by Henry Kucera and Nelson Francis of Computational Analysis of Present-Day American English in 1967, a work based on the analysis of the Brown Corpus, a carefully compiled selection of current American English, totalling about a million words drawn from a wide variety of sources. Kucera and Francis subjected it to a variety of computational analyses, from which they compiled a rich and variegated opus, combining elements of linguistics, language teaching, psychology, statistics, and sociology.

Shortly thereafter Boston publisher Houghton-Mifflin approached Kucera to supply a million word, three-line citation base for its new American Heritage Dictionary, the first dictionary to be compiled using corpus linguistics. The AHD made the innovative step of combining prescriptive elements (how language should be used) with descriptive information (how it actually is used).

Other publishers followed suit. The British publisher Collins' COBUILD dictionaries, designed for users learning English as a foreign language, were compiled using the Bank of English.

The Brown Corpus has also spawned a number of similarly structured corpora: the LOB Corpus (1960s British English), Kolhapur (Indian English), Wellington (New Zealand English), ACE (Australian English), the Frown Corpus (early 1990s American English), and the FLOB Corpus (1990s British English). Other corpora represent many languages, varieties and modes, and include The British National Corpus, a 100 million word collection of a range of spoken and written texts, created in the 1990s by a consortium of publishers, universities (Oxford and Lancaster) and the British Library. There is a project underway to create an American National Corpus.