Product Code Database
An n-gram is a sequence of n adjacent symbols in a particular order. (2025). 9780121709600 ISBN 9780121709600 The symbols may be n adjacent letters (including and blanks), , or rarely whole found in a language dataset; or adjacent extracted from a speech-recording dataset, or adjacent base pairs extracted from a genome. They are collected from a text corpus or speech corpus.
If Latin numerical prefixes are used, then n-gram of size 1 is called a "unigram", size 2 a "bigram" (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, Greek numerical prefixes 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 or of a known size, called k-mer. When the items are words, -grams may also be called shingles.
In the context of natural language processing (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.
| + Figure 1. n-gram examples from various disciplines ! Field !! Unit !!Sample sequence !! 1-gram sequence !! 2-gram sequence !! 3-gram sequence |
| ..., Cys-Gly-Leu, Gly-Leu-Ser, Leu-Ser-Trp, ... |
| ..., AGC, GCT, CTT, TTC, TCG, CGA, ... |
| ..., to_, o_b, _be, be_, e_o, _or, or_, r_n, _no, not, ot_, t_t, _to, to_, o_b, _be, ... |
| ..., to be or, be or not, or not to, not to be, ... |
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
4-grams
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