1 (often foll. by on, upon) be controlled or determined by (success depends on hard work; it depends on whether they agree; it depends how you tackle the problem).
2 (foll. by on, upon) a be unable to do without (depends on her mother). b rely on (I'm depending on you to come).
3 (foll. by on, upon) be grammatically dependent on.
4 (often foll. by from) archaic poet. hang down.
Phrases and idioms:
depend upon it! you may be sure! it (or it all or that) depends expressing uncertainty or qualification in answering a question (Will they come? It depends).
Etymology: ME f. OF dependre ult. f. L dependere (as DE-, pendere hang)
Useful english dictionary. 2012.