I
In zoology, one of a pair of slender, segmented sensory organs on the head of centipedes , millipedes ), and crustaceans .
Antennae of insects, which are movable, are believed to serve as both tactual and smell receptors; in some species, the development of elaborate antennal plumes and brushlike terminations has led to the suggestion that they also serve for hearing. Evidence supports this idea only for the mosquito , whose antennae are attached to specialized structures stimulated by vibrations of the antennal shaft. In social insects (e.g., ants ), antennae movements may serve as communication.
II
or aerial
Component of radio , television , and radar systems that directs incoming and outgoing radio waves.
Usually of metal, antennas range in shape and size from the mastlike devices used for radio and television broadcasting to the large parabolic reflectors used to focus satellite signals and the radio waves generated by distant astronomical objects and reflect them toward the centrally located receiver. Antennas were invented in the 1880s by {{link=Hertz, Heinrich Rudolf">Heinrich Hertz ; Guglielmo Marconi made many improvements.