The paper studies the polyfunctionality of the English connective as, “connective” being used with reference to a clause linkage device (or conjunction). In Modern English, the item in question functions as a coordinating conjunction and subordinating conjunction of comparison, manner, time, cause, purpose, condition, concession. Thus, the paper aims to bring to light some of the problems connected with the semantic and pragmatic ambiguity of the connective as well as give a brief pragmatic account of the diachronic development of its meanings using the framework of relevance theory, subjectification theory and the invited inference theory of semantic change. The analysis is conducted using the data from modern British fiction and scientific prose as well as from Old, Middle and Early Modern English. Using various tests, the author shows that the aforementioned meanings of as are cases of semantic polysemy. There is also evidence suggesting that causal as is a pragmatically ambiguous item (the ambiguity exists between the epistemic and speech act domains).