因|いんin[1]atamadaka (head-high)

1. nouncause; factor
2. noun, Buddhismhetu (direct cause, esp. as opposed to indirect conditions)
3. nounthe basis of one's argument (in hetuvidya)

• Synonym原因げんいんNeutralThe most general word for cause, as in 「事故の原因」; 「因」 is rarely used on its own and mostly appears as a morpheme in 「勝因」「死因」.
• Synonym要因よういんWrittenWritten/formal: the main cause or factor, analytical in tone, as in 「成功の要因」; 「因」 mostly serves as a morpheme.
• Synonym因子いんしWrittenWritten/formal and academic: the individual factors that make up a result; also a divisor in mathematics.
• SynonymファクターNeutralA loanword for factor or element, frequent in business and academic use; 「因」 leans toward the direct cause.
• Related素因そいんWrittenWritten/formal: an underlying, root cause; in medicine, a predisposition. 「因」 is the general word for a cause.
• Related要素ようそNeutralA component or element making something up, not necessarily a cause; 「因」 is about causes or the basis of an argument.
• Related元もとNeutralThe origin or source of something, common in everyday speech, as in 「風邪の元」; 「因」 is written/formal and rarely used alone.
• Related誘因ゆういんWrittenWritten/formal: a trigger or motive that induces something, as in 「事故の誘因」; 「因」 is the general word for cause.
• RelatedエレメントNeutralLoanword for element or component, used mainly in technical fields; it does not express cause.
• Antonym果てはてNeutralThe end or the final outcome things arrive at, as in 「挙げ句の果て」; it contrasts with 「因」 only in the cause-then-effect sense.
• Antonym果かNeutralAs an antonym it takes the result, outcome sense, as in 「議論の果てに」; in Buddhism the counterpart of 「因」 is 「果」, as in 「因果」.

For cause in general, use 「原因」; for analyzing factors, 「要因」. 「因」 on its own is written/formal and mostly serves as a morpheme in 「勝因」「死因」; Buddhism says 「因果」, and in hetuvidya it means the basis of an argument.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

1. （イン）原因げんいん。
2. （イン）（縁えん・果かに対たいして）直接ちょくせつの原因げんいん。