Definition

Noun: A pair of consecutive written units, most commonly two consecutive letters, within a sequence of text. In computational linguistics and natural language processing, it is a fundamental unit for statistical analysis, often used to model the probability of character or word sequences.

Usage

A "bigram" is used to analyze the frequency and patterns of letter or word pairs. It is a technical term central to text analysis, cryptography, and language modeling. - In letter-level analysis, it refers to any two adjacent characters (e.g., "th" in "the"). - In word-level analysis, it refers to any two adjacent words (e.g., "black cat" in the phrase "a black cat").

Examples

• Letter Bigram:
  • The word "hello" contains the letter bigrams: "he", "el", "ll", "lo".
  • In English, the bigram "th" is one of the most frequent.
• Word Bigram:
  • The sentence "I like apples" contains the word bigrams: "I like" and "like apples".
  • Analyzing word bigrams helps predict the next likely word in a sentence.

Advanced Usage

• Statistical Language Modeling: Bigram models calculate the probability of a word given the previous word (P(word{n-1})). This is a simple but foundational type of N-gram model.
• Cryptanalysis: Studying letter bigram frequencies (like "qu", "ed") is a classic technique for breaking substitution ciphers.
• Text Prediction & Autocomplete: Systems often use bigram probabilities to suggest the next word as you type.

Variants and Related Words

• N-gram: A sequence of consecutive items (letters, syllables, words). A bigram is an N-gram where n=2.
• Trigram: A sequence of three consecutive items (n=3).
• Unigram: A single item sequence (n=1).
• Bigrammatic (adj): Pertaining to or consisting of bigrams.

Synonyms

• Digram (less common, sometimes used interchangeably in specific contexts like cryptography).
• 2-gram (a more technical synonym used in computational fields).

Related Phrases/Concepts

• Bigram Frequency: The count of how often a specific pair of letters or words appears in a corpus.
• Bigram Probability: The conditional probability of the second unit given the first.
• Bigram Collocation: A pair of words that frequently occur together (e.g., "high school", "traffic light").

Noun

1. a word that is written with two letters in an alphabetic writing system