exactphrase

Exact phrase refers to a type of search query in information retrieval where the document must contain a specific sequence of words in the given order, with no intervening terms. It is used when the exact wording matters, such as quotes, titles, or precise technical phrases. This differs from general keyword searches, which may return documents containing any of the terms in any order, and from proximity queries, which allow a bounded gap between words.

Implementation typically relies on a positional inverted index, where each term is indexed with the positions at which it occurs in a document. A phrase query checks for a sequence of positions where the terms appear consecutively in the correct order. This requires careful tokenization and often normalization steps, such as case folding and punctuation handling. Some systems also apply stemming or stop-word removal, which can affect exact phrase matching; to preserve exactness, these steps may be restricted for the query or the indexing process.

Variants include allowing a small amount of slop (gaps) in the sequence, which enables near-exact or near-match phrase searches, versus strict exact phrases with zero tolerance. The choice depends on the search application and user expectations.

Applications extend across search engines, digital libraries, and data systems where precise wording is important, such as legal documents, scientific abstracts, or literary quotations. Common examples include using quoted phrases in user queries and implementing dedicated phrase queries in search platforms like Elasticsearch or other full-text engines.