1. A turn: one's opportunity to do something that not everyone can do at the same time.

2. A queue, a line: a sequence of people waiting for their turn to do something (either a physical line in which they stand, or a metaphorical one).

3. An appointment: a scheduled time to do something. (colloquial)

4. period (a geochronologic unit of millions to tens of millions of years; a subdivision of an era, and subdivided into epochs) (geology)

5. period (a length of time in history seen as a single coherent entity; an epoch, era)

6. turtle-dove