A friend is your buddy, your pal, your amigo, your comrade. You know, someone you trust and like enough to hang out with on a regular basis.
The noun friend comes to us from the Old English word freond. Back then you had to be careful to not confuse freond with feond, which meant “fiend or enemy.” These days it's pretty tough to get mixed up though. Friends are the people you can count on, the ones that make you laugh and throw you birthday parties. Enemies are generally the mean ones.