严肃
yánsù · HSK 5
serious
严 = strict + 肃 = solemn; together = serious, solemn
严 carries the sense of strict or stern, and 肃 means solemn or respectful. Stacked together they describe a grave, serious manner — the kind of tone used at formal ceremonies or stern warnings.
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.