Compositionality Principle

In semantics, the Compositionality Principle is a principle (attributed to Frege, hence sometimes called Frege's Principle) that constrains the relation between form and meaning by requiring that the meaning of a composite expression is built up from the meanings of its basic expressions.

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This principle plays an important role in formal semantic theories, like Montague Grammar. Here the Compositionality Principle takes the form of a homomorphism, a mapping that assigns meanings to the basic expressions of the language and semantic operations to syntactic rules.

Link
Utrecht Lexicon of Linguistics