leading tone vs subtonic

leading tone and subtonic both are nouns.

Word	Noun	Adjective	Verb	Adverb
leading tone	Yes	No	No	No
subtonic	Yes	No	No	No

As nouns, leading tone and subtonic are synonyms defined as:

leading tone and subtonic: (music) the seventh note of the diatonic scale

leading tone (noun)	subtonic (noun)
(music) the seventh note of the diatonic scale	(music) the seventh note of the diatonic scale