noun which may take the genitive case particle 'no'
primary; first-occurrence
Medical term used to describe a condition, disease, or disorder that arises spontaneously or is not caused by another condition. Often contrasted with 二次性 (secondary).
Primary hypertension often has no identifiable cause.
It is necessary to determine whether this symptom is primary or secondary.
Compound of 一次 (いちじ, 'first, primary') + 性 (せい, 'nature, -ity'). The term is a modern medical coinage following the pattern of 二次性 (secondary).