A postcard is a thing - a message card you send in the mail. All "things" are nouns. Postcard is a noun.
part of speech
The part of speech for this particular word is a noun.
The part of speech for "answer" is a noun.
adverb
what part of speech is beneath
a metered postcard is a postcard that already has the stamp made into the the postcard. there is no need to put an adhesive stamp on it.
The part of speech for "explicit" is an adjective.
The part of speech for "twirl" is a verb.
The part of speech for "unfamiliar" is an adjective.
The part of speech of "came" is a verb.
The part of speech for "lecturer" is a noun.
The part of speech for "indefinite" is an adjective.