relative pitch
Relative pitch is the ability to correctly sing a melody line, following musical notation, by pitching each note in the melody according to its distance from the previous note; this may include or be applied to sight reading. Relative pitch may also refer to the ability to hear a melody for the first time and name the notes relative to some known starting pitch, and/or the ability to identify the intervals between given tones (e.g. a fifth or an octave), or the distance of a musical note from a set point of reference (e.g. three octaves above middle C).
Unlike perfect pitch, relative pitch is common amongst non-musicians and can be developed through ear training.