严禁
yán jìn · HSK 7
to strictly prohibit
🚫 严 strict/stern + 禁 prohibit = a strict prohibition
严 means strict or stern (think 严格 strict), and 禁 means to ban or forbid (as in 禁止). Stack them and you get a strong, official prohibition: strictly forbidden.
严 — mouth 口 (top) + cliff 厂 + 敢 (phonetic)
严 (traditional 嚴) originally depicted shouting mouths 吅 over a cliff 厂 with 敢 'dare' as the phonetic, suggesting a stern command issued from on high. The core meaning shifted from 'urgent shouting' to 'strict, severe, solemn'. The simplified form 严 keeps the top mouth and cliff while dropping most of the phonetic.