hardsub vs subtitle

hardsub and subtitle both are nouns.

Word	Noun	Adjective	Verb	Adverb
hardsub	Yes	No	No	No
subtitle	Yes	No	Yes	No

As nouns, subtitle is a hypernym of hardsub; that is, subtitle is a word with a broader meaning than hardsub:

hardsub: (often plural) a subtitle whose text is irreversibly merged in original video frames.
subtitle: translation of foreign dialogue of a movie or TV program; usually displayed at the bottom of the screen

Other hypernyms of hardsub include caption.

hardsub (noun)	subtitle (noun)
(often plural) a subtitle whose text is irreversibly merged in original video frames.	secondary or explanatory title
	translation of foreign dialogue of a movie or TV program; usually displayed at the bottom of the screen

hardsub (verb)	subtitle (verb)
	supply (a movie) with subtitles