厳禁

1. Origins, structure, and basic meaning

• Structure: 厳禁 (げんきん) is a nominal predicate expressing an emphatic formal prohibition.
• Basic usage: 無断立入は厳禁だ makes unauthorized entry the topic of a full predication, while 火気厳禁 compresses a ban on open flames into sign language.

2. Common pitfalls and similar expressions

• Full predication and compressed signage
  • 厳禁だ is a predicate closed by だ, whereas 火気厳禁 is compressed signage with particles omitted. The latter is not a subject–verb statement in which fire performs the banning.