Antenna and Flagellum

Antenna noun - One of a pair of mobile appendages on the head of e.g. insects and crustaceans; typically sensitive to touch and taste.

Flagellum and antenna are semantically related. In some cases you can replace term "Flagellum" with "Antenna", this nouns are similar.

Flagellum noun - A lash-like appendage used for locomotion (e.g., in sperm cells and some bacteria and protozoa).

Antenna and flagellum are semantically related. Sometimes you can use "Antenna" instead a noun "Flagellum".