ˈaktə̇n noun
( -s )
Etymology: International Scientific Vocabulary act- (from Latin actus motion) + -in; originally formed as German aktin — more at act
: a protein in muscle that is active in muscular contraction, is separable from the muscle structure along with myosin by use of strong salt solutions in the presence of adenosine triphosphate, and is known in both globular and fibrous forms