from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. Any function whose value repeats after the regular addition of a period to its independent variable; i.e. f(x+t) = f(x) for some t over all x
from the GNU version of the Collaborative International Dictionary of English
- adj. a function whose values recur at fixed intervals as the variable uniformly increases. The trigonomertic functions, as sin x, tan x, etc., are periodic functions. Exponential functions are also periodic, having an imaginary period, and the elliptic functions have not only a real but an imaginary period, and are hence called doubly periodic.
Sorry, no etymologies found.