"Since" marks the specific point when something started; "for" indicates how long something has lasted.
Preposition. Marks the starting point of an action or state that is still true. Followed by a specific moment in time: a date, an event, a year. "Desde" in Spanish.
She has lived in Madrid since 2018.
Ella ha vivido en Madrid desde 2018.
I have known him since we were children.
Lo conozco desde que eramos ninos.
He has not eaten since breakfast.
El no ha comido desde el desayuno.
Preposition. Indicates the total duration of an action or state. Followed by a period of time: hours, days, months, years. "Desde hace" or "durante" in Spanish.
She has lived in Madrid for six years.
Ella ha vivido en Madrid desde hace seis anos.
I have known him for most of my life.
Lo conozco desde hace la mayor parte de mi vida.
He has not eaten for twelve hours.
El no ha comido en doce horas.
Common mistake
Classic error: "I have studied English since three years." Wrong — "since" needs a point in time (2021, Monday, I was a child), not a duration. Correct: "I have studied English for three years." Another error: "I have lived here for 2020." Wrong — "for" needs a duration (three years), not a point in time. Correct: "I have lived here since 2020."
Trick to remember it
Ask yourself: does what follows indicate a point in time or a duration of time? Point in time (2019, Monday, when I was a child) = since. Duration of time (three years, two weeks, five months) = for. Spanish clue: "desde [point]" = since, "desde hace [duration]" = for. Quick test: can you answer "how long?" with a number? Use for. Can you answer "when did it start?" with a date or event? Use since.
Quick rule
Since + point in time (2020, Monday). For + duration (three years, two days).
Did you know?
"Since" and "for" are used mainly with perfect tenses (present perfect, past perfect). "I lived there for ten years" (simple past, completed period) is also correct. But "I lived there since 2010" is odd — if the action continues to today, use present perfect: "I have lived there since 2010." And "since" can be a conjunction: "Since you are here, can you help me?" — there it does not mark time but cause (given that, because).
Exercise 1 · Pick the right one
She has worked at that company _____ fifteen years.
Exercise 2 · Pick the right one
He has not spoken to his brother _____ their argument last Christmas.
Exercise 3 · Form the word
Since + point in time (2020, Monday). For + duration (three years, two days).
Classic error: "I have studied English since three years." Wrong — "since" needs a point in time (2021, Monday, I was a child), not a duration. Correct: "I have studied English for three years." Another error: "I have lived here for 2020." Wrong — "for" needs a duration (three years), not a point in time. Correct: "I have lived here since 2020."
Ask yourself: does what follows indicate a point in time or a duration of time? Point in time (2019, Monday, when I was a child) = since. Duration of time (three years, two weeks, five months) = for. Spanish clue: "desde [point]" = since, "desde hace [duration]" = for. Quick test: can you answer "how long?" with a number? Use for. Can you answer "when did it start?" with a date or event? Use since.
Bryan López
Founder of SpeakUP Academy