Music Bass (rhyming with "face") when used as an adjective, describes tones which are of low frequency. Played in an ensemble such notes are frequently used to provide a counterpoint or counter-melody, in an harmonic context either to outline or juxtapose the progression of the chords, or with percussion to underline the rhythm.
It can also refer to a male singer with the lowest range in music. A typical bass will have a range extended from around the F one and a half ovtaves below middle C (the note at the bottom of the bass clef) to the E above middle C (on the first line of the treble clef).
In classical music, and particularly in opera, there are sometimes distinctions made between different kinds of basses. A basso profondo (or basse noble) is a singer with a particularly deep voice; they may be able to get as low as the B below the bass clef. By contrast, a basso cantate (or basse chantate) is a singer with a lighter, more lyrical voice, perhaps with a slightly higher range. Basso buffo is a term used for a comic bass.
The male voice a little higher than a bass is the baritone. Sometimes the term bass-baritone is used to mean a singer with a range and tone somewhere between a bass and a baritone.