ONE[always before noun]›only one: There was a single light in the corner of the room.
every single›used to emphasize that you are talking about each one of a group or series: I call him every single day.He could hear every single word we said.
MARRIAGE›not married: He's young and single.
PARENT[always before noun]›looking after your children alone without a partner or the children's other parent: a single mothera single-parent family