definition 1: to trust or depend (usually followed by “on” or “upon”).
example: I hope I can rely on your confidentiality in this matter.
example: I need a baby sitter that I can really rely on.
example: After her accident, she had to rely on her family to take care of her.
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Note on use: How does the verb “rely” compare with the verb “depend”?
“Rely” and “depend” can be said to have the same meaning with respect to definition 1 above, but “rely” is most comfortably used with respect to trusting in the honesty, discretion, or authority of another individual. The first example above is a particularly apt one for “rely.” “Depend” seems to be used more often than “rely” in connection with receiving needed support or help from another. It may simply be that “rely” tends to be used in connection with more abstract notions. In general “depend” is a more common word than “rely,” but this is partly because it has an additional, very common meaning that “rely” does not have, as in the sentence “Arriving on time will depend on the weather.” Both “depend” and “rely” must be followed by “on” or “upon” when followed by an object (e.g., rely on one’s friends, rely on one’s lawyer, rely on someone’s advice).