A familiar, affectionate suffix attached to names (often for children, close friends, or pets) expressing closeness or endearment; not used in formal contexts.
太郎ちゃんは幼稚園で人気者だ。
Taro-chan is popular at kindergarten.
犬のポチちゃんが庭で遊んでいる。
Our dog Pochi-chan is playing in the yard.
ちゃん付けは親しい相手に使う呼び方だ。
Adding -chan is a way to address someone you are close to.
上司に『ちゃん』と呼ぶのは失礼だ。
It's rude to call your boss with -chan.