How to say "Serious" in Japanese

When translating "serious" into Japanese, you must choose carefully between 重大 and 謹厳. In Japanese, 重大 (じゅうだい (jūdai)) is typically associated with "Serious, grave, important, significant" (Syllabus Level: N3) and represents Emphasizes the importance, gravity, or severity of a matter. Often used for problems, decisions, news. Can be used with な as an adjective. On the other hand, 謹厳 (きんげん (kingen)) maps to "serious; solemn; grave; strict; austere" (Syllabus Level: N1) and represents Describes a person's character, attitude, or appearance as being very serious, strict, and formal, often implying a lack of humor or lightheartedness. 真面目で厳格な態度や様子を指す。. A literal translation of "serious" can often sound unnatural to native Japanese speakers if mixed up!