taru-adjective, adverb taking the 'to' particle, na-adjective
calm; composed; self-possessed
Describes a person's deep, unshakable calmness or composure, often with a literary or classical flavor. Used in the form 深沈とした or 深沈としている.
彼は深沈とした態度で、どんな困難にも動じなかった。
With a deeply composed demeanor, he remained unshaken by any difficulty.
adverb taking the 'to' particle, taru-adjective
silently (of the passing of the night); quietly
Used to describe the deep, quiet stillness of night passing. Appears in classical or poetic contexts, often as 深沈と更ける or similar expressions.
夜は深沈と更けていった。
The night deepened silently.
The exact derivation is uncertain. The kanji 深 (deep) and 沈 (sink, quiet) combine to suggest profound stillness or composure. The reading しんちん is the on'yomi of the characters.