noun, noun which may take the genitive case particle 'no'
main cause; primary factor
Refers to the principal reason or contributing element behind a situation, often used in analytical, scientific, or news contexts.
The main cause of the accident was excessive speed.
成功の要因を分析する。
Analyze the primary factors behind the success.
The weak yen became a factor in the increase in exports.
Experts analyzed the factors behind the accident.
An investigation was conducted to find out the factors behind the decline in performance.
The declining birth rate is a major factor in the economic stagnation.
要因 refers to any contributing factor in an analysis, whereas 主因 designates the single dominant factor.
要因 is a neutral term for any contributing factor (positive or negative), while 誘因 specifically emphasizes a factor that provokes or triggers something, often negative like disease or crisis.
要因 is a neutral term for a contributing factor or cause, while 決め手 specifically singles out the factor that clinches or decides the outcome.
proximate cause
positive factor; contributing factor