actin

noun ac·tin \ ˈak-tən \

Definition of actin

: a cellular protein found especially in microfilaments (such as those comprising myofibrils) and active in muscular contraction, cellular movement, and maintenance of cell shape

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Recent Examples of actin from the Web

Like a pasta maker, the scale cell squeezes out and assembles a lattice of actins.

— gwen pearson, WIRED, "How Butterflies Get Their Shine," 22 Dec. 2014

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'actin.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Origin and Etymology of actin

probably from ²act or act(ivate) + ¹-in

NEW! Time Traveler

First Known Use: 1942

in the meaning defined above

See Words from the same year

actin-

combining form

variants: or actini- or actino-

Definition of actin-

1 : having a radiate form

actinolite

2 : actinic radiation (such as X-rays)

actinometer

Origin and Etymology of actin-

borrowed from Greek aktino-, from aktīn-, aktís "ray, beam, spoke of a wheel"

Note: The Greek word has traditionally been linked with Sanskrit aktú-, conjectured to mean "twilight," and with Germanic *uŋhtwōn- "last part of the night, dawn," whence Old English ūhte "twilight, daybreak," Old High German uohta "dawn," Old Norse ōtta "last part of the night," Gothic uhtwo "dawn," from Indo-European *n̥k^wt-u-n-, a zero-grade derivative of *nok^wt-/*nek^wt- "night" (see ¹night). Robert Beekes (Etymological Dictionary of Greek, Leiden, 2009) rejects this connection on the grounds that aktís "shows no trace of a labiovelar." In reference to actinic radiation, the formative actino- was probably first used by John herschel in actinometer (1833).

Medical Dictionary

actin

noun ac·tin \ ˈak-tən \

medical Definition of actin

: a protein found especially in microfilaments (as those comprising myofibrils) and active in muscular contraction, cellular movement, and maintenance of cell shape — see f-actin, g-actin