A number of objects or events arranged or coming one after the other in succession. A set of stamps, coins, or currency issued in a particular period. Physics & Chemistry A group of objects related by linearly varying successive differences in form or configuration: a radioactive decay series; the paraffin alkane series. Mathematics The sum of a sequentially ordered finite or infinite set of terms. Geology A group of rock formations closely related in time of origin and distinct as a group from other formations. Grammar A succession of coordinate elements in a sentence. A succession of usually continuously numbered issues or volumes of a publication, published with related authors or subjects and similar formats. A succession of regularly aired television programs, each one of which is complete in and of itself. Sports A number of games played by the same two teams, often in succession. Baseball The World Series. Linguistics A set of vowels or diphthongs related by ablaut, as in sing, sang, sung, and song. in series In an arrangement that forms a series.