Crawled properties are metadata that is extracted from documents during crawls. Metadata can be structured content (such as the title or the author from a Word document), or unstructured content (such as a detected language or extracted keywords).
Users can only search on managed properties and not on crawled properties. To make a crawled property available for search queries, you must map the crawled property to a managed property. You can map multiple crawled properties to a single managed property or map a single crawled property to multiple managed properties
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