metrical unit vs metrical foot

metrical unit and metrical foot both are nouns.

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

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

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

Other synonyms of metrical unit include foot.

metrical unit (noun)	metrical foot (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