noun, noun which may take the genitive case particle 'no'
fixed number; certain number; given number; definite number
Refers to a specific, predetermined, or agreed-upon quantity. Often used in contexts like quotas, thresholds, or statistical counts.
応募者が一定数に達したら締め切ります。
We will close applications once we reach a certain number of applicants.
この実験には一定数のサンプルが必要だ。
This experiment requires a fixed number of samples.
多数 means 'a large number' or 'many', without the sense of being predetermined or fixed.
Compound of 一定 (fixed, certain) and 数 (number).