tachograph vs tach

tachograph and tach both are nouns.

Word	Noun	Adjective	Verb	Adverb
tachograph	Yes	No	No	No
tach	Yes	No	No	No

As nouns, tach is a hypernym of tachograph; that is, tach is a word with a broader meaning than tachograph:

tachograph: a tachometer that produces a graphical record of its readings; used to record the speed and duration of trips in a motor vehicle
tach: measuring instrument for indicating speed of rotation

Other hypernyms of tachograph include tachometer.

tachograph (noun)	tach (noun)
a tachometer that produces a graphical record of its readings; used to record the speed and duration of trips in a motor vehicle	measuring instrument for indicating speed of rotation