The 7th of any chord or change is the b7, always. That's why all maj 7's are qualified as such. Major 7 always implies leading tone. C7, Cm7, C+7 (C7#5), Cm7b5, Cdim, all have a b7. Cmaj7, Cmmaj7 have a leading tone, which is major 7. The seventh in terms of language, always implies b7. Seven by itself in terms of language, always implies leading tone.