Used when someone is taking over another's duties or role temporarily or permanently. I'll be singing in her stead at the concert, since she lost her voice.
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Impersonal Tone
The phrase often implies a formal or distant relationship with the person being replaced. His counsel will be acting in his stead during the trial.
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Historical Use
Frequently found in historical or literary contexts, suggesting a traditional tone. The knight fought in his lord's stead in the joust.