to trust; to have confidence in; to depend.
"I always rely on my sister to help me when I am sick because she is so kind and dependable."
In plain English: To rely on someone means to trust them enough that you count on their help when you need it.
"I always rely on my friend to pick me up from work when I finish early."
Usage: Use rely on when indicating dependence or placing trust in someone, as the preposition is required after this verb. Avoid confusing it with similar words like count on by noting that both imply reliance but differ slightly in formality and certainty of expectation.
The word rely comes from the Old French relier, which originally meant to "fasten" or "bind." It traveled into English with this sense of securing something firmly before evolving to mean depending on someone's trustworthiness.