(mathematical analysis) Any expression that represents the addition a countably infinite number of ordered summands, often explicitly indexed by the positive or nonnegative integers.

The promotional or advertisement term used to describe the final episode of a television program, usually a situation comedy or a drama.

(narratology) The first published narrative in a series of works; a narrative from which later narratives are written after. It serves as the chronological core of the series.

(chemistry) A list of the metals in order of their electronegativity (and hence their reactivity).

(chemistry) any series of aliphatic organic compounds whose members differ only in the addition of a CH₂ group; for example, the carboxylic acids, CH₃(CH₂)ₙCOOH where n is any whole number

(US, baseball) The best-of-seven game series played annually in late October-early November to determine the year's championship of professional baseball in the United States and Canada, played between two teams, one each in the National League and the American League.

(chemistry) any group of elements whose chemical and physical properties have similarities, and that vary progressively through the series; evident within the periodic table

Any electric circuit having all elements joined in a sequence such that the same current flows through them all

(mathematics) Any power series such that the ratio of the (k+1)-th and the k-th terms is a rational function of the natural integer k.

(number theory) Any infinite series of the form ∑ₙ₌₁ ᪲(a_n)/(nˢ), where s and each a_n are complex numbers.