someone who is on their own. they are simply one, and will never be fully completed by someone else. they like to be alone most of the time, and get irritated easily by other people. they enjoy the company of the opposite sex, but mostly for pleasure and conversation.
if someone calls you on the phone or messages you, and says something like this: "i was just wondering if you wanted to come chill for a bit.. just you& me ? .. maybe watch a movie or something ?".. that means they are deifnitely a singular. they also might add on a .."no strings attached".