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What is declaration merging?

Q: What is declaration merging?

**Declaration merging** lets multiple declarations with the same name combine into one definition. Two `interface` declarations with the same name merge their members — useful for augmenting third-party types or extending global interfaces (e.g. adding a property to `Window`). `type` aliases cannot be merged this way.

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interface-merging

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Declaration merging lets multiple declarations with the same name combine into one definition. Two interface declarations with the same name merge their members — useful for augmenting third-party types or extending global interfaces (e.g. adding a property to Window). type aliases cannot be merged this way.

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