Friendship related words:
1. a best friend:
(often used by children) to describe the person they are closest to. A 'best friend' is usually your best friend for life
2. a close friend:
a good friend
3. a pal:
(informal): a friend
4. a mate:
(informal): a friend
5. a girlfriend:
a girl or woman who is your platonic friend or a girl or woman you have a romantic relationship with
6. a boyfriend:
a boy or man you have a romantic relationship with
7. an acquaintance:
person who isn't a friend but someone you know a little