Depending On (Varies With)
3 related grammar points that express the same core idea - compared below so you can tell which one to reach for.
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に応じて / 次第で / 次第です
The outcome is not yet decided and hinges on one factor.
～次第で vs ～に応じて: Use 次第で: 天気次第で中止. It makes the factor decisive for something still open. に応じて describes adjusting in proportion to a factor (収入に応じて), which is a response, not a verdict waiting to be reached.
Closing a formal explanation by saying what the matter rests on.
～次第です vs ～次第で: 次第です is the polite sentence-final form used to round off an explanation. 次第で sits mid-sentence with the outcome following it. Same word, and the choice is only whether the sentence ends there.