solemn
adjective uk/ˈsɒl.əm/ us/ˈsɑː.ləm/
庄严的，严肃的
serious and without any humour
a solemn face/voice 严肃的脸／声音
solemn music 严肃音乐
Everyone looked very solemn. 大家看上去都很严肃。
solemn promise, commitment, undertaking, etc. 郑重承诺
an agreement that you make in a serious way and expect to keep