primary tooth vs milk tooth

primary tooth and milk tooth both are nouns.

Word	Noun	Adjective	Verb	Adverb
primary tooth	Yes	No	No	No
milk tooth	Yes	No	No	No

As nouns, primary tooth and milk tooth are synonyms defined as:

primary tooth and milk tooth: one of the first temporary teeth of a young mammal (one of 20 in children)

Other synonyms of primary tooth include baby tooth, deciduous tooth.

primary tooth (noun)	milk tooth (noun)
one of the first temporary teeth of a young mammal (one of 20 in children)	one of the first temporary teeth of a young mammal (one of 20 in children)