The article presents a corpus-based empirical analysis of colloquial units in contemporary English, treating colloquial vocabulary as a dynamic, multifunctional, and internally heterogeneous subsystem of the lexical system. Colloquial units are examined not merely as markers of informal speech, but as linguistically significant elements reflecting ongoing transformations in communicative practices, discourse conventions, and stylistic norms. Drawing on data from large-scale, register-diverse English language corpora, the study investigates the frequency, dispersion, contextual variability, and pragmatic functions of selected colloquial units across spoken and written registers. Special attention is paid to processes of stylistic diffusion, pragmatic refunctionalization, and partial desemanticization.