"Depend" expresses uncertainty or condition; "rely" expresses firm trust in someone or something.
To depend on an uncertain condition, or to need something/someone. Always followed by "on".
Whether we go to the beach depends on the weather.
Si vamos a la playa depende del clima.
It depends — what time are you planning to leave?
Depende. ¿A que hora piensas salir?
Children depend on their parents for everything in the early years.
Los ninos dependen de sus padres para todo en los primeros anos.
To firmly trust in something or someone. Implies that person or thing is dependable. Followed by "on".
You can rely on her. She always keeps her promises.
Puedes confiar en ella. Siempre cumple sus promesas.
I rely on public transport to get to work every day.
Dependo del transporte publico para ir al trabajo todos los dias.
Do not rely solely on one source of income.
No dependas de una sola fuente de ingresos.
Common mistake
Using "depend" when you want to express confidence in a reliable person. "I depend on her" is correct (I need her) but "You can depend on her" and "You can rely on her" are both fine. The difference is that "rely on" implies she IS trustworthy, while "depend on" may only imply that you need her (perhaps too much). "Rely on" has a more positive connotation.
Trick to remember it
Connotation clue: "rely" always has a positive connotation of trust. "I rely on my team" = I trust my team, they are dependable. "Depend" can be neutral or negative: "She depends too much on others" = she is too dependent. If you want to praise someone's reliability, use "rely". If you are talking about an uncertain condition, use "depend".
Quick rule
Depend on = to be conditional on / to need (neutral). Rely on = to firmly trust (positive).
Did you know?
"Reliable" comes from "rely" + "-able". "Dependable" comes from "depend" + "-able". Interestingly, as adjectives both form nearly synonymous words used interchangeably: "a reliable car" = "a dependable car". But the verbs diverge more in use. Reliability as a quality unites them; verbal usage distinguishes them.
Exercise 1 · Pick the right one
Whether I take the job _____ on the salary they offer.
Exercise 2 · Pick the right one
You can _____ on Marcus. He never misses a deadline.
Exercise 3 · Form the word
Depend on = to be conditional on / to need (neutral). Rely on = to firmly trust (positive).
Using "depend" when you want to express confidence in a reliable person. "I depend on her" is correct (I need her) but "You can depend on her" and "You can rely on her" are both fine. The difference is that "rely on" implies she IS trustworthy, while "depend on" may only imply that you need her (perhaps too much). "Rely on" has a more positive connotation.
Connotation clue: "rely" always has a positive connotation of trust. "I rely on my team" = I trust my team, they are dependable. "Depend" can be neutral or negative: "She depends too much on others" = she is too dependent. If you want to praise someone's reliability, use "rely". If you are talking about an uncertain condition, use "depend".
Bryan López
Founder of SpeakUP Academy