The words in, on and at can express
location (where something is). Something is in
a large place such as a country, city, town or village:
I was in Nigeria. She's in Manchester.
Something is on a street:
It's on Castle Street.
Something is at an address:
My house is at twelve Castle Street. I am at Peter's house. (or simply
I am at Peter's.)
The general pattern here is that in is used with
larger things, on with medium-sized things, and at
with smaller things. But the reality is more complicated,
because in and on express other ideas too.
In expresses the idea of being inside something,
in its interior, surrounded by it. Thus we can say:
I'm at the house. (I might be inside the house, in the
garden, or on the street just outside.)
I'm in the house. (I am inside the house.)
On expresses the idea of being attached to the outside
of something, touching its surface but not penetrating inside:
I spilt water on the table. (The water is touching the outside of the table.)
There was a spider on the wall. (It is touching the outside of the wall.)
Compare these sentences:
I got mud on my shoe. (The mud is clinging to the outside of
the shoe, but the inside is clean.)
I got mud in my shoe. (The mud has entered the shoe and
made my socks wet and muddy too.)
There are rats on the walls. (The rats are climbing on the
surfaces of the walls.)
There are rats in the walls. (The walls are hollow, and
the rats move about inside them.)
There is a pen on the desk. (It is lying on the surface of
the desk.)
There is a pen in the desk. (It is inside the desk, and one
must open the desk to find it.)
We say on a planet or on a moon because the things we
discuss on planets or moons tend to be on the surface. Note this
contrast of in and on:
There are higher animals on the Earth's surface, but deep
in the Earth's crust the only things that can live are bacteria.
We also use on for small islands, even though these are
usually larger than towns:
I'm on the Isle of Todday.
On is used for unnamed contients, but named continents
use in:
It's on the continent. On which continent is it?
It's in Europe. It's in Central America.
Direction: To, Toward(s), In, On,
Into, Onto, At
The most usual preposition to express direction of movement is to:
I was travelling to London. (I was moving in the direction of London)
We are on a train to Glasgow. (the train moving in the direction of Glasgow)
Toward (also towards) is also very common:
I was driving toward London. (I was moving in the direction of London)
Generally, to indicates that the traveller will arrive at the destination, but with
toward(s) this may not be so:
I drove to Cardiff. (I arrived in Cardiff at the end)
I drove towards Cardiff for several miles, then turned off onto a side road. (I started moving
in the direction of Cardiff, but before reaching Cardiff I turned aside)
I threw the ball to Anne. (the ball reached Anne and she caught it)
I threw the ball toward Anne, but it fell short and landed on the ground.
(the ball moved in the direction of Anne but it did not reach her)
If something ends its movement touching the outside of a thing, then we often use on or
onto:
The snow fell on/onto my car. (after falling, the snow touched the outside of my car, not the inside)
If something ends its movement within the inside of a thing, then we often use in or
into:
I went in/into the house. (I finished my movement within the house)
at often indicates an intention to hit something:
I threw the ball at Anne. (I intended the ball to hit her)
I threw the ball to Anne. (I intended Anne to catch the ball)
