悪い

1. Origins, structure, and basic meaning

• Structure: 悪い(わるい) is an い-adjective describing a bad condition or fault attributable to someone.
• Basic usage: 天気が悪い describes a condition, while 私が悪かった accepts blame or fault.

2. Common pitfalls and similar expressions

• Meaning from context
  • Translate it as “bad” for weather or conditions and as “at fault” when responsibility is involved.
• Past form
  • Its past form is 悪かった; do not form it like a noun or な-adjective.