Sentence:  When "A" is a set in the ordinary sense of the term, its membership function can take on only two values 0 and 1, with "f<sub>A</sub>(x)" = 1 or 0 <WSD>according as</WSD> "x" does or does not belong to "A". 
Meaning of the word marked with <WSD> tags:  Precisely as; the same as; corresponding to the way in which. (Now often expressing accordance with two or more alternatives.) (from 16th c.)