the odd one out

US /ðɪ ˌɑːd wʌn ˈaʊt/
UK /ðɪ ˌɑːd wʌn ˈaʊt/
"the odd one out" picture
1.

異質なもの, 仲間外れ, 変わり者

a person or thing that is different from or excluded from others in a group or series

:
In this group of fruits, the apple is the odd one out because all the others are berries.
この果物のグループでは、他のすべてがベリーなので、リンゴが異質なものです。
He always felt like the odd one out in his family because he was the only artist.
彼は家族の中で唯一の芸術家だったので、いつも異質な存在だと感じていた。