严密
yán mì · HSK 7
strict
🔒 严 strict/severe + 密 dense/secret = tightly sealed, no gaps
严 means strict or severe; 密 means dense or secret (same 密 as in 秘密 secret). Together: so tightly packed there is no gap — used for airtight organization or close surveillance.
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.
密 — 宀 roof + 必 (phonetic) + 山 mountain
Originally referring to a hidden, sheltered place in the mountains, 密 combines 宀 (roof/cover) over 必 (phonetic) with 山 (mountain) at the base. The meaning extended from 'secluded mountain hideaway' to 'dense, close, secret'. Today it commonly means dense, intimate, or secret.