servomechanical vs servo

servomechanical is not a noun while servo is a noun.

Word	Noun	Adjective	Verb	Adverb
servomechanical	No	Yes	No	No
servo	Yes	Yes	No	No

As adjectives, servomechanical and servo are synonyms defined as:

servomechanical (noun)	servo (noun)
	control system that converts a small mechanical motion into one requiring much greater power; may include a negative feedback system

servomechanical (adjective)	servo (adjective)
of or involving servomechanisms	of or involving servomechanisms