The appendage of the third cephalon somite, consisting of a five-segmented peduncle and a flagellum. Through fusion of the segments with the body or with each other, the peduncle may seem to consist of fewer segments. The flagellum is usually multi-articulated, it may be supple or very stiff; in the Scyllaridae the flagellum is transformed into a single plate-like segment, similar to the peduncular segments. The antenna sometimes is named "second antenna", and the antennula, "first antenna". Both, the antenna and the antennula are tactile organs (feelers).

Alternative form for antenna : antennae.