As simple adv.: for that reason, thus, therefore; ?also, with indefinite force: for any reason [quot. c1390].

As interrog. adv. in direct questions: (a) for what reason?, on account of what?, why?; ~ and whi, whi and (or) ~; ~ that; (b) in elliptical or truncated constructions: what is the reason for it?; as ~; (c) in phrase: ~ is, what has become of (sth.)? [cp. wher adv. & conj. 2a.(b)].

As rel. adv. introducing adj. clauses [sometimes difficult to distinguish from sense 4a.]: (a) with ref. to circumstances, actions, situations, etc. presented as causes or occasions of subsequent events: on account of which, because of which, in consequence of which; ?also, by means of which, through which; also with ellipsis of verb in the subordinate clause; ~ that; cause (resoun, skil) ~; whi and ~; (b) with verbs or verb phrases expressing notions of emotional response, recompense, etc.: in return for which, at which, for which; (c) with ref. to a person or God presented as the focus of one’s efforts or travels: for whom, toward whom; (d) with ref. to a place presented as an origin: whence, of which.

As subordinating conj. introducing adv. clauses, often with diminished force: (a) with ref. to an action, a particular circumstance, a specific situation, etc.: on account of which action, which thing having been done, because of the doing of which, for which reason; be hit ~ so hit ever be, for whatsoever reason it may be; also in correlation with pleonastic ther-fore [quot. c1400(?c1390)]; (b) with ref. to a set of premises, a series of logical propositions, an argument, etc.: on the basis of which, whence it is that; (c) with very loose ref., as a transitional device with mild causal force, a means of advancing a narrative implying temporal consequentiality rather than strict causality, a formulaic link between items, etc.: and so, and therefore, hence; also with ellipsis of the verb in the subordinate clause [quot. a1400]; (d) ?with ref. to a following circumstance presented as the reason for the main predication: because, since; (e) with ref. to an action or a circumstance presented as a means or an occasion: such that, to the end that, thus bringing it about that; (f) in locative use, with generalizing force: in whatever place, wherever; ~ sum-ever.

As subordinating conj. introducing noun clauses or inf. phrases usu. functioning as direct obj. of verb or verb phrase: (a) with verbs of intellection, perception, or communication: for what reason, on what account, why; also functioning as subj., extraposed subj., or appositive; ~ that; whi (hou, whanne) and ~; (b) with other verbs: that for which, what…for; also functioning as appositive to subj. [quot. c1400]; (c) functioning as subj. or pred. nom. with ben v.: the reason that (sth. is so); ~ that; (d) in indirect questions: for what reason, on what account, why; ~ that; asken (apposen) ~; (e) don ~, to provide, or provide to (sb.), compensation or payment in return for something; (f) in elliptical or truncated constructions: the reason for that, the reason why; also functioning as extraposed subj. [quot. a1500(?c1450)] or appositive; ~ ne whi, whi (hou)…and ~.