One of a pair of jointed limbs on the head of various arthropods.
Antennule (A1): first pair of antennae in Crustacea in particular.
Antenna (A2): second cephalic appendage or first pair of oral limbs in Copepods.

Alternative forms for antenna : A1, A2, antennae, antennal, antennulary, antennule, antennules.