同類

1. Origins, structure, and basic meaning

• Structure: 同類 (どうるい) is a noun for things or people of the same kind or a similar group.
• Basic usage: It describes checking whether plants belong together or people being judged as the same kind because of another's wrongdoing.
  • 二つの植物が同類かどうか確かめるため、葉の形を比べた。 — We compared leaf shapes to determine whether the two plants were related.
  • 一人の不正のせいで、仲間まで同類だと思われた。 — One person's wrongdoing caused colleagues to be seen as the same kind.

2. Common pitfalls and similar expressions

• Classification and negative association
  • 同類 can be a neutral classification or, by context, a negative judgment grouping someone with a wrongdoer.