Depending on its usage in a sentence, it could be many different things, a noun, an adjective or an adverb as I can think of them.
Adjective:
The elderly lady walked down the street
Adverb:
She began to realize that she had become elderly
Noun:
The elderly in our community deserve more respect.
part of speech
Adjective
What part of speech is thaw
The part of speech for oscillate is verb.
An adjective is a part of speech.
The elderly woman is on a fixed income. Here, fixed is an adjective. He fixed the broken television. Here, fixed is a verb.
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
Old Major, the wise elderly pig, has a speech.
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.