actuator vs positioner

actuator and positioner both are nouns.

Word	Noun	Adjective	Verb	Adverb
actuator	Yes	No	No	No
positioner	Yes	No	No	No

As nouns, positioner is a hyponym of actuator; that is, positioner is a word with a more specific, narrower meaning than actuator:

actuator: a mechanism that puts something into automatic action
positioner: (computer science) the actuator that moves a read/write head to the proper data track

Other hyponyms of actuator include rotary actuator, hydraulic motor.

actuator (noun)	positioner (noun)
a mechanism that puts something into automatic action	(computer science) the actuator that moves a read/write head to the proper data track
	a device used to control the opening or closing of the actuator based on electric, or pneumatic signals.