This is the 1568th most frequent Japanese word.
友
"Friend."
Here, 友 is used in a vocative case, addressing the person as 'friend' directly, showing closeness or rapport.
友よ、困った時は私に連絡して下さい。
Friend, please contact me if you are in trouble.
Here, 友 is part of the word 友達, meaning 'friends,' indicating companionship or friendship.
友達と映画を見に行きました。
I went to watch a movie with my friend.
In this sentence, 友 is used directly to refer to 'friend' as a singular noun, emphasizing personal relationship.