Longman Dictionary of Contemporary English - rely

~ v rely on/upon sb/sth phr v 1 to trust someone or something to do what you need or expect them to do  (rely on sb/sth to do sth)  (I think we can rely on Derek not to tell anyone. | rely on sb/sth doing sth)  (You can't just rely on your parents lending you the money. | rely on sb/sth for sth)  (Tim always relies on his wife for advice on clothes) 2 to depend on something in order to continue to live or exist  (rely on sth/sb for)  (They have to rely on the river for their water.)