Add: [A.] [2.]A.2 c.A.2.c Math. Of a set: containing no elements; = null a. 4 c. Also applied transf. to other entities, esp. in Computing. Opp. *non-empty a.    1937 Jrnl. Symbolic Logic II. 67 A set or class is said to be empty if there is no element of it.    1946 A. Weil Found. Algebraic Geom. iv. 84 The bunch of varieties defined by an empty set of varieties will be called empty.    1966 [see injective a.].    1981 A. Chandor Penguin Dict. Microprocessors 130 Null string, a string with no characters. Also known as empty string.