Series  n. (pl. Same) 1 number of similar or related things, events, etc.; succession, row, or set. 2 set of related but individual programmes. 3 set of related geological strata. 4 arrangement of the twelve notes of the chromatic scale as a basis for serial music. 5 set of electrical circuits or components arranged so that the same current passes through each successively.  in series in ordered succession. [latin sero join]