n.
Variant: or actini- or actino-
Function: combining form
Etymology: New Latin, ray, from Greek aktin-, aktino-, from aktin-, aktis; perhaps akin to Old English ū hte morning twilight, Latin noct-, nox night ― more at NIGHT
1 : having a radiate form < actino lite>
2 : actinic radiation (as X rays) < actino meter>