駄目

1. Origins, structure, and basic meaning

• Structure: 駄目 is read as だめ and is a noun and na-adjectival expression meaning not allowed or no good and ineffective.
• Basic usage: Photography being prohibited appears in 写真を撮っては駄目だ, while repeated repairs being useless appears in 何度修理しても駄目だ.

2. Common pitfalls and similar expressions

• Prohibition and failure
  • ては駄目 expresses prohibition, while ても駄目 after an attempt means it did not work.
• Difference from いけない
  • Both can express prohibition, but this word also commonly evaluates an object or method as useless or unsuccessful.