Other forms: depending, depends, depended
Depend means you cannot manage without something. A baby depends on its parents for everything, a village depends on one bus a day, and the whole plan depends on the weather.
It takes ON or UPON and nothing else — depend on me, never depend of me and never depend me. Its second use is about what decides an outcome: whether we walk depends on the rain. On its own, 'it depends' is a complete answer in English, and 'that depends' buys you a moment before you commit to anything. The adjective is dependent, as in dependent on aid, and the noun is dependence or dependency — while a dependant with an A is a person you support. Depending on makes a useful opener too: depending on the traffic, we will be there by six.
1verbdependTo need someone or something in order to manage.
“The charity depends on donations from a few hundred people.”
synonyms: rely, lean on
2verbdecidedTo be decided by something else.
“How long it takes depends on how many people turn up.”
Too few real examples of this word to estimate which sense is commonest.
Also accepted in games: rely
Before depend arrived, English had its own word for this idea: hangian. The borrowed verb pushed the native one aside, which is the usual fate of a plain English word when a Latin-shaped rival turns up.
Latin
dependeō
Old French
dependre
Middle English
dependen
English, today
depend
From Middle English dependen, from Old French dependre, from Latin dependeō. In this sense, displaced native hangian.
Etymology from Wiktionary, CC BY-SA