English phraseological units (multi-word expressions such as idioms, collocations, proverbs, etc.) can be classified by integrating their syntactic structure and degree of semantic compositionality. This theoretical article proposes a structured taxonomy that cross-classifies phraseological units by formal syntactic pattern (e.g. verb–object combinations, adjective–noun collocations, binomial phrases, clausal proverbs) and by semantic transparency (ranging from fully non-compositional idioms to partially compositional idioms, conventional collocations, and pragmatically fixed formulas or pragmatemes). Drawing on phraseological research and Meaning–Text Theory, we distinguish categories like full idioms (holistic, non-literal meanings), semi-idioms (partially analyzable metaphoric expressions), collocations (compositional yet convention-bound word combinations), and pragmatemes (fixed expressions tied to specific pragmatic contexts). Illustrative examples are provided for each category alongside clear classification criteria. The taxonomy accounts for structural diversity (from fixed noun phrases to whole proverbs) while highlighting the continuum of compositionality. The discussion addresses implications for linguistic analysis, cross-linguistic comparison (with brief reference to Azerbaijani equivalents), and theoretical modeling of the lexicon. This integrative classification aims to enhance our understanding of phraseological units, benefiting lexicology, semantics, syntax, and phraseology research by offering a comprehensive framework for describing multi-word expressions in English.
Hasan Alisoy (2025) studied this question.