Second (disambiguation)

Second stands for:
 a unit for time; See: Second
 Two is the second positive whole number. 
 Arcsecond, a unit of angle
 Second of right ascension, in astronomy
 Second (parliamentary procedure), to support a proposal
 Second, the agent of a participant in a duel or a cornerman in combative sports such as boxing
Music
 Diminished second, or unison
 Minor second, or semitone
 Neutral second, or three-quarters-tone (i.e., one-and-a-half semitones)
 Major second, or whole tone (i.e., two semitones)