ESEN
Which one to use?Beginnerstructurestructure
InvsOn
'In' goes with broad periods, 'on' with specific days and dates, 'at' with exact moments; think of decreasing time size.
Side-by-side comparison
In
structureGeneral rule: "in" for long periods (months, years, seasons), "on" for specific days and dates, "at" for exact times and precise moments.
My birthday is in July, this year I am planning a small party with close friends.
She was born in 1998 and grew up in a small town in the south of Spain.
In the morning I like to have a coffee and read the news before I start work.
On
structureCommon exceptions: "at night", "at the weekend" (British English), "in the morning/afternoon/evening", "on time". These combinations need to be memorized.
The concert is on Friday evening, we need to leave by seven to get there on time.
She always calls her parents on Christmas Day, no matter where she is in the world.
The train leaves at 8:15, be on the platform at least five minutes before it departs.
Common mistake
The most common errors: "ON the morning" (correct: "in the morning"), "AT Monday" (correct: "on Monday"), "IN 9 o'clock" (correct: "at 9"), "ON next Monday" (correct: no preposition: "next Monday"), and "IN night" (correct: "at night").
Trick to remember it
Three-size rule: IN = large (month, year, century, part of day). ON = medium (day of the week, specific date). AT = small/exact (exact time, holiday period). Main exception: "at night" (never "in night"). Next/last/this + time = no preposition.
Quick rule
- •IN: months, years, seasons, parts of the day.
- •ON: days, specific dates, special days.
- •AT: times, noon, midnight, holiday periods, "at night." No preposition: next/last/this Monday/year/morning.
Did you know?
IN/ON/AT for time is one of the most searched topics on Google by English learners worldwide. The reason it is so difficult for Spanish speakers is that Spanish mainly uses just two prepositions for time: "en" and "a", where English uses three with different rules. "En enero" = IN January. "El lunes" = ON Monday (different preposition, no article). "A las 9" = AT 9. Most confusing of all: some expressions take NO preposition in English ("last Monday") when Spanish uses one ("el lunes pasado"). Linguists call prepositions one of the most idiomatic aspects of any language because their use can rarely be deduced by pure logic, they must be learned in context.
Practise what you learned
Exercise 1 · Pick the right one
We usually have a big family dinner _____ Christmas.
Exercise 2 · Pick the right one
I was born _____ a Tuesday morning in November.
Exercise 3 · Form the word
Related word pairs
InvsOn / At
'In' goes with broad periods; 'on' goes with specific days and dates; 'at' goes with exact moments.
InvsOn / At
'In' means inside a space; 'on' means on a surface; 'at' indicates a specific point or location.
In timevsOn time
"On time" = punctual, exactly at the scheduled time; "in time" = with enough time, before it is too late.
AvsAn
'A' is used before consonant sounds; 'an' is used before vowel sounds.
Bryan López
Founder of SpeakUP Academy