Since vs for — time prepositions — englishillustrated.com

Since vs For: The Key Difference

Both 'since' and 'for' talk about time, but they work differently. Use 'since' to say WHEN something started—the starting point in time. Use 'for' to say HOW LONG something lasted—the duration or length of time. For example: 'I have lived here since 2015' (starting point) but 'I have lived here for 8 years' (duration).

Side-by-Side Comparison

SINCE answers 'when did it start?' and is followed by a specific time (a year, date, or time expression). FOR answers 'how long?' and is followed by a time period (hours, days, months, years). Both are commonly used with the present perfect tense ('have/has + past participle') to connect the past to now.

Since vs For: At a Glance

Dimension	Since	For
Form	since + point in time (a specific moment, date, or event)	for + period of time (a duration or length of time)
Question answered	Since when? — marks the starting point of an action or state that continues to the present	How long? — expresses the total amount of time an action or state has lasted
What follows	A specific point: a year (since 2010), a date (since Monday), an event (since the meeting), or a clause (since I was a child)	A measured span: for two hours, for a week, for several months, for ages
Positive example	"She has lived in Paris since* 2018."* "I have known him since* we were teenagers."*	"She has lived in Paris for* six years."* "I have known him for* a long time."*
Negative example	"I haven't eaten since* breakfast."* "He hasn't called since* last Tuesday."*	"I haven't eaten for* eight hours."* "He hasn't called for* a week."*
Question example	"Since* when have you been learning Spanish?"* "How long has it been since* you last slept?"*	"How long have you been learning Spanish for?" "Have you been waiting for* a long time?"*
Typical tenses used with	Primarily present perfect and present perfect continuous; also past perfect when referring to an earlier period	Present perfect, present perfect continuous, past simple, past continuous, and future tenses — used across a wider range of tenses
Key signal words / time expressions	since yesterday, since noon, since 1999, since January, since last summer, since the beginning, since then, since I was born	for two days, for an hour, for three weeks, for a month, for years, for a long time, for ages, for centuries
Common learner errors	❌ "I have lived here since ten years." ✅ "I have lived here since 2014." — do not use since with a duration	❌ "I have lived here for last year." ✅ "I have lived here for a year." — do not use for with a specific point in time
💡 Key Difference: Use since to pinpoint the starting moment of an ongoing situation (e.g., a date, event, or named time). Use for to describe the total length of that situation (e.g., a number of hours, days, or years). A simple test: if you can answer the question "Since when?", use since; if you can answer "How long?" with a measured span, use for.