selector

Someone or something which selects or chooses.
An administrator responsible for selecting which players will play for a side.
A matching expression in a stylesheet determining which elements in the markup are affected by a style.
A pointer to a structure describing a segment of memory.
(Internet, historical) A text string transmitted to a Gopher server, identifying the resource to be retrieved.
A disc jockey.
(Australia, historical) A person who is entitled to choose a tract of Crown land to purchase.