selector

Short definition from Wiktionary

Noun

1. 1
   Someone or something which selects or chooses.
2. 2
   An administrator responsible for selecting which players will play for a side.
3. 3
   A matching expression in a stylesheet determining which elements in the markup are affected by a style.
4. 4
   A pointer to a structure describing a segment of memory.
5. 5
   A text string transmitted to a Gopher server, identifying the resource to be retrieved.
6. 6
   A disc jockey.
7. 7
   A person who is entitled to choose a tract of Crown land to purchase.