noun
lack of faith; unbelief; impiety; infidelity
Refers to the absence or rejection of religious faith, or a state of not believing. Often used in religious or moral contexts.
彼の不信仰は家族を悲しませた。
His lack of faith saddened his family.
不信仰は罪だと教えられた。
I was taught that unbelief is a sin.
無信仰 also means 'lack of faith' but can imply a more neutral absence of religion, while 不信仰 often carries a negative moral judgment.
Compound of 不 (fu, 'not') + 信仰 (shinkō, 'faith, belief'). The prefix 不 negates the following noun, forming a straightforward antonym.