domestic dog vs doggie

domestic dog and doggie both are nouns.

Word	Noun	Adjective	Verb	Adverb
domestic dog	Yes	No	No	No
doggie	Yes	No	No	No

As nouns, doggie is a hyponym of domestic dog; that is, doggie is a word with a more specific, narrower meaning than domestic dog:

domestic dog: a member of the genus Canis (probably descended from the common wolf) that has been domesticated by man since prehistoric times; occurs in many breeds
doggie: informal terms for dogs

domestic dog (noun)	doggie (noun)
a member of the genus Canis (probably descended from the common wolf) that has been domesticated by man since prehistoric times; occurs in many breeds	informal terms for dogs