adjective Not accompanied by anything else; one in number.
Can you give me a single reason not to leave right now?
adjective Not divided in parts.
The potatoes left the spoon and landed in a single big lump on the plate.
adjective Designed for the use of only one.
a single room
adjective Performed by one person, or one on each side.
a single combat
adjective Not married, and (in modern times) not dating or without a significant other.
Forms often ask if a person is single, married, divorced, or widowed. In this context, a person who is dating someone but who has never married puts "single".
adjective Having only one rank or row of petals.
adjective Simple and honest; sincere, without deceit.