To fix, settle, standardize, or make something uniform — to set or establish a standard or stable state.
温度を一定に保つために空調を調整した。
I adjusted the air conditioning to keep the temperature constant.
基準を一定するには多くの議論が必要だ。
It takes a lot of discussion to set standards consistently.
実験条件を一定にしないと結果が比較できない。
If experimental conditions aren't kept constant, results can't be compared.
Fixed, definite, or constant — used to indicate something defined, uniform, or a certain/established amount or level (e.g., 一定の～).
一定の条件を満たせば補助金が受けられる。
If you meet certain conditions, you can receive a subsidy.
彼の能力は一定して高い。
His ability is consistently high.
賃金は一定ではなく、業績によって変わる。
Wages are not fixed and vary depending on performance.