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to fix; to settle; to standardize; to regularize
constant; definite; uniform; defined; certain; prescribed
この会社は一定の給料が保証されている。
This company guarantees a fixed salary.
温度を一定に保つことが実験の鍵だ。
Keeping the temperature constant is key to the experiment.
品質を一定に保つのは難しい。
Keeping quality consistent is difficult.