A casual, often shortened or affectionate name used in place of a person's real name. Common in informal contexts.
彼のニックネームは「タカ」です。
His nickname is 'Taka'.
友達にはニックネームで呼ばれている。
I'm called by my nickname by my friends.
His classmates gave him the nickname 'Octopus'.
All my friends call me by my nickname.