John-
It's my understanding (often flawed I admit) that the "bare" seventh chord (talking about the full four note chord) R7 is properly described as a "dominant" seventh chord: root + major third + perfect fifth + minor seventh; the "minor seventh" notated as rm7 describes a minor triad plus the minor seventh: root + minor third + perfect fifth + minor seventh; the "major seventh" Rmaj7 or RM7 is a major triad plus the major seventh.
These conventions derive mostly from the classical contexts of scales and keys, and don't always make sense if we're just throwing around disembodied chords.
Cheers
-Glenn