metrical foot vs metrical unit

metrical foot and metrical unit both are nouns.

Word	Noun	Adjective	Verb	Adverb
metrical foot	Yes	No	No	No
metrical unit	Yes	No	No	No

As nouns, metrical foot and metrical unit are synonyms defined as:

metrical foot and metrical unit: (prosody) a group of 2 or 3 syllables forming the basic unit of poetic rhythm

Other synonyms of metrical foot include foot.

metrical foot (noun)	metrical unit (noun)
(prosody) a group of 2 or 3 syllables forming the basic unit of poetic rhythm	(prosody) a group of 2 or 3 syllables forming the basic unit of poetic rhythm