Loner (noun)

1. A person who prefers not to associate with others.
2. A person who is alone or solitary.

Origin:

Mid 16th century (as a noun denoting a person who lives alone): from lone + -er.

Examples:

1. He was always a bit of a loner and preferred his own company.
2. She was known as a loner, who kept to herself and never mingled with others.
3. The loner sat in the corner of the room, observing everyone but not participating in the conversation.
4. He was a loner by nature and always felt more comfortable alone.
5. Many people thought he was a loner but he was actually just shy.