subtonic vs leading tone

subtonic and leading tone both are nouns.

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

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

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

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