When to use In, On and At

One of the themes that most raises doubts in those who study English are prepositions (prepositions). As in the Portuguese language, prepositions in English are also used to link elements of the sentence.

In,on and until are prepositions used to refer mainly to time and place.

See below when to use in, on and until:


In is a preposition used to indicate time and place. Its meaning depends on the context to which it applies, for example, "within", "in", "from", "in" and "in".

time indication

With regard to time, we can say that in is used to indicate longer and less defined time periods, such as, a part of the day, one month, one year, etc.

Look at the examples:

part of the day: in the afternoon (in the afternoon)

I study English in the afternoon. (I study English in the afternoon.)

Exception: when the part of the day is night, it is used until and not in: The show will be at night. (The show will be at night.)

Indication of one year: in 1999 (in 1999)

she was born in 1999. (She was born in 1999.)

One month indication: in june (in June)

His birthday is in June. (His birthday is in June.)

See too Date in English and Months of the year in English.

Seasons: in the winter (In the winter)

we love to travel in the winter. (We love traveling in winter.)

indication of place

When referring to a place, we must use the preposition in when we talk about bigger places like cities, countries, States, parts of a house, etc.

Look at the examples:

City: in Rio de Janeiro (in Rio de Janeiro)

They live in Rio de Janeiro. (They live in Rio de Janeiro.)

Parents: in Brazil (in Brazil)

He has a company in Brazil. (He has a company in Brazil.)

Part of the house: in the living room (in the room)

We prefer to watch TV in the living room. (We prefer to watch TV in the living room.)


on is a preposition used to refer mainly to dates and specific days and the local surfaces.

as with in, it can be translated in different ways depending on the context of the sentence to which it is applied.

Their meanings can vary, for example, from "over", "over", "above", "in", "in" and "in".

time indication

Let's look at some examples of using the preposition on to reference specific dates and days:

Specific date: on October 6th. (on October 6th)

My boyfriend's birthday is on October 6th. (My boyfriend's birthday is October 6th.)

specific day: on mondays (on mondays)

The boys play soccer on Mondays. (Boys play football on Mondays.)

indication of place

Note the use of the preposition on to reference locations surfaces

  • The fruits are on the table. (The fruits are on the table.)
  • The book is on the shelf. (The book is on the shelf.)

NOTE: we also use the preposition on with some electronic media, for example: on the phone (on the phone), on the internet (on the Internet); and with some means of public transport, for example, on the bus (in the bus), on the plane (on the plane) and on the subway (in the subway).


At is a preposition used in expressions that indicate schedules, moments and specific locations. Depending on the context in which it belongs, it can mean "à(s)", "in", "in" and "in".

time indication

See below for the use of the preposition until indicating times:

  • The meeting will begin at 10 am. (The meeting will start at 10 am.)
  • Our flight arrived at nine o’ clock. (Our flight arrived at nine o'clock.)

indication of place

  • My brother is at home. (My brother is at home.)
  • We had lunch at school yesterday. (We had lunch at school yesterday.)


Below you will find a diagram with the uses of each of these propositions:


Check the expressions used in the diagram:

In the 21st century (in the 21st century)

In the 1990s (In the 90's)

In 2012 (In 2012)

In February (In February)

In the morning (In the morning)

In the afternoon (In the afternoon)

In the evening

on monday (On Monday)

on the 25th (on the 25th)

on February 25th (On February 25th)

on christmas day (On Christmas Day / At Christmas)

on easter day (On Easter day/On Easter)

on new Year's Day (On New Year's Day/On New Year's)

At noon (By noon)

At Midnight (At midnight)

At 7 o'clock (At 7 o'clock)

At 7:30 am (at 7:30 am)

At christmas (At Christmas)

At easter (In Easter)

At New Year's (On New Year)

Complement your studies with the texts below.

  • English prepositions
  • Genitive case
  • The most used phrasal verbs in English
  • The 10 most used conjunctions in English
  • To and For

Entrance Exam Questions

1. (UNESP-1986) Check the correct alternative:

Fried potatoes are called “French Fries” __________ the United States.

a) on
b) about
c) of
d) from
e) in

Alternative e) in

2. (UFPE) Some 63,000 of the boat people have wound up ____________ the British crown colony of Hong Kong, …

a) in
b) across
c) on
d) behind
e) over

Alternative a) in

3. (Fuvest-adapted) Complete with the required words:

I was born __________ 2 o'clock __________ the morning, __________ to Sunday __________ April __________ the year 1958, on a farm in a small village called Sta. Cruz, in the state of Goiás, Brazil.

a) on / in / on / in / in
b) on / in / on / in / of
c) at / in / on / in / of
d) at / in / in / in / of

Alternative c) at / in / on / in / of

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