An ''n''-gram is a sequence of ''n'' adjacent symbols in particular order. The symbols may be ''n'' adjacent

letters Letter, letters, or literature may refer to: Characters typeface * Letter (alphabet), a character representing one or more of the sounds used in speech or none in the case of a silent letter; any of the symbols of an alphabet * Letterform, the g ...

(including

punctuation mark Punctuation marks are marks indicating how a piece of written text should be read (silently or aloud) and, consequently, understood. The oldest known examples of punctuation marks were found in the Mesha Stele from the 9th century BC, consisti ...

s and blanks),

syllable A syllable is a basic unit of organization within a sequence of speech sounds, such as within a word, typically defined by linguists as a ''nucleus'' (most often a vowel) with optional sounds before or after that nucleus (''margins'', which are ...

s, or rarely whole

word A word is a basic element of language that carries semantics, meaning, can be used on its own, and is uninterruptible. Despite the fact that language speakers often have an intuitive grasp of what a word is, there is no consensus among linguist ...

s found in a language dataset; or adjacent

phoneme A phoneme () is any set of similar Phone (phonetics), speech sounds that are perceptually regarded by the speakers of a language as a single basic sound—a smallest possible Phonetics, phonetic unit—that helps distinguish one word fr ...

s extracted from a speech-recording dataset, or adjacent base pairs extracted from a genome. They are collected from a

text corpus In linguistics and natural language processing, a corpus (: corpora) or text corpus is a dataset, consisting of natively digital and older, digitalized, language resources, either annotated or unannotated. Annotated, they have been used in corp ...

speech corpus A speech corpus (or spoken corpus) is a database of speech audio files and text Transcription (linguistics), transcriptions. In speech technology, speech corpora are used, among other things, to create acoustic models (which can then be used with ...

. If Latin numerical prefixes are used, then ''n''-gram of size 1 is called a "unigram", size 2 a "

bigram A bigram or digram is a sequence of two adjacent elements from a string of tokens, which are typically letters, syllables, or words. A bigram is an ''n''-gram for ''n''=2. The frequency distribution of every bigram in a string is commonly used f ...

" (or, less commonly, a "digram") etc. If, instead of the Latin ones, the English cardinal numbers are furtherly used, then they are called "four-gram", "five-gram", etc. Similarly, using

Greek numerical prefixes Numeral or number prefixes are prefixes derived from numerals or occasionally other numbers. In English and many other languages, they are used to coin numerous series of words. For example: *triangle, quadrilateral, pentagon, hexagon, octagon ...

such as "monomer", "dimer", "trimer", "tetramer", "pentamer", etc., or English cardinal numbers, "one-mer", "two-mer", "three-mer", etc. are used in computational biology, for

polymer A polymer () is a chemical substance, substance or material that consists of very large molecules, or macromolecules, that are constituted by many repeat unit, repeating subunits derived from one or more species of monomers. Due to their br ...

s or

oligomer In chemistry and biochemistry, an oligomer () is a molecule that consists of a few repeating units which could be derived, actually or conceptually, from smaller molecules, monomers.Quote: ''Oligomer molecule: A molecule of intermediate relativ ...

s of a known size, called ''k''-mers. When the items are words, -grams may also be called ''shingles''. In the context of

natural language processing Natural language processing (NLP) is a subfield of computer science and especially artificial intelligence. It is primarily concerned with providing computers with the ability to process data encoded in natural language and is thus closely related ...

(NLP), the use of ''n''-grams allows bag-of-words models to capture information such as word order, which would not be possible in the traditional bag of words setting.

Examples

(Shannon 1951) discussed ''n''-gram models of English. For example: * 3-gram character model (random draw based on the probabilities of each trigram): ''in no ist lat whey cratict froure birs grocid pondenome of demonstures of the retagin is regiactiona of cre'' * 2-gram word model (random draw of words taking into account their transition probabilities): ''the head and in frontal attack on an english writer that the character of this point is therefore another method for the letters that the time of who ever told the problem for an unexpected'' Figure 1 shows several example sequences and the corresponding 1-gram, 2-gram and 3-gram sequences. Here are further examples; these are word-level 3-grams and 4-grams (and counts of the number of times they appeared) from the Google ''n''-gram corpus. 3-grams * ceramics collectables collectibles (55) * ceramics collectables fine (130) * ceramics collected by (52) * ceramics collectible pottery (50) * ceramics collectibles cooking (45) 4-grams * serve as the incoming (92) * serve as the incubator (99) * serve as the independent (794) * serve as the index (223) * serve as the indication (72) * serve as the indicator (120)

References

External links

Ngram Extractor: Gives weight of ''n''-gram based on their frequency.

Google's Google Books ''n''-gram viewer
an

(September 2006)
STATOPERATOR N-grams Project Weighted ''n''-gram viewer for every domain in Alexa Top 1M

1,000,000 most frequent 2,3,4,5-grams
from the 425 million word

Corpus of Contemporary American English The Corpus of Contemporary American English (COCA) is a one-billion-word corpus of contemporary American English. It was created by Mark Davies, retired professor of corpus linguistics at Brigham Young University (BYU). Content The Corpus of C ...

Peachnote's music ngram viewer

Stochastic Language Models (''n''-Gram) Specification
(W3C)
Michael Collins's notes on ''n''-Gram Language Models

OpenRefine: Clustering In Depth
{{Natural Language Processing Natural language processing Computational linguistics Language modeling Speech recognition Corpus linguistics Probabilistic models

Examples

References

Further reading

See also

External links