Supplement \Sup"ple*ment\, n. [F. suppl['e]ment, L. supplementum, fr. supplere to fill up. See Supply, v. t.]

1. That which supplies a deficiency, or meets a want; a store; a supply. [Obs.]

--Chapman.

2. That which fills up, completes, or makes an addition to, something already organized, arranged, or set apart; specifically, a part added to, or issued as a continuation of, a book or paper, to make good its deficiencies or correct its errors.

3. (Trig.) The number of degrees which, if added to a specified arc, make it 180[deg]; the quantity by which an arc or an angle falls short of 180 degrees, or an arc falls short of a semicircle.

Syn: Appendix.

Usage: Appendix, Supplement. An appendix is that which is appended to something, but is not essential to its completeness; a supplement is that which supplements, or serves to complete or make perfect, that to which it is added.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Supplement \Sup"ple*ment\, v. t. [imp. & p. p. Supplemented; p. pr. & vb. n. Supplementing.]

To fill up or supply by addition; to add something to.

Causes of one kind must be supplemented by bringing to bear upon them a causation of another kind. --I. Taylor.

Source: Webster's Revised Unabridged Dictionary (1913)