In, On, At — Fixed Expressions — English Grammar Exercises
In, on, at and beyond — master spatial prepositions
Fixed Expressions with In, On, and At
Beyond the spatial logic, English has dozens of fixed prepositional expressions that must be memorised. The British National Corpus shows that fixed-expression preposition errors are the most common preposition mistake type in intermediate learner writing — learners apply spatial logic to expressions that have become idiomatic. The most error-prone pairs are 'on fire' vs 'in fire', 'on sale' vs 'at sale', and 'in danger' vs 'on danger'.
Fixed Expressions with 'On'
- on fire — burning
- on sale — available at a reduced price
- on the phone — engaged in a call
- on the coast / on a river — along a geographical edge
- on the second floor — floors are always surfaces
All winter coats are on sale this week. (not 'at')
She's been on the phone for an hour. (not 'in')
Fixed Expressions with 'In'
- in danger — at risk
- in trouble — having serious problems
- in the queue — waiting in a line
- in bed — sleeping or resting
There were fifty people in the queue. (not 'on')
Fixed Expressions with 'At'
- at a distance — from a distance
- at work / at home / at school — at a functional location
Common Mistakes
✗ Nobody was on danger. → ✓ Nobody was in danger.
✗ She arrived in the airport. → ✓ She arrived at the airport.
✗ She called me at her phone. → ✓ She called me on her phone.
Frequently Asked Questions
What is the difference between 'in', 'on', and 'at' for place?
'In' describes enclosed or bounded spaces where you are surrounded: 'in the garden', 'in a box', 'in bed'. 'On' describes surfaces, lines, and edges where things rest or are attached: 'on the table', 'on the floor', 'on the coast'. 'At' marks a specific point on the map — a meeting place, building entrance, or precise location: 'at the bus stop', 'at the station', 'at the end of the street'. Islands use 'on' (treated as a surface); cities use 'in'; specific buildings use 'at'.
What is the difference between 'above' and 'over', and between 'below' and 'under'?
'Over' implies close proximity or coverage — directly above, often touching or moving across: 'She pulled the blanket over her head', 'The bridge goes over the river'. 'Above' is more abstract — simply higher than, without implying coverage: 'The plane flew above the clouds', 'a painting above the fireplace'. Similarly, 'under' places something directly beneath a physical object ('under the bed'), while 'below' describes a lower position on a scale or in general space ('below the average', 'below zero', 'below sea level').
When do I use 'between' and when 'among'?
'Between' is used with two specific, individually identified items: 'the pharmacy is between the bank and the post office'. 'Among' is used with a group of three or more, or an undifferentiated mass: 'I found my keys among all the papers'. A common error is using 'between' for crowds or collective nouns — 'she was sitting among the crowd' (not 'between').
What is the difference between 'across' and 'through'?
'Across' means from one side to the other of a flat or two-dimensional surface: 'across the road', 'across the bridge', 'across the field'. 'Through' means moving inside a three-dimensional, enclosed space from one end to the other: 'through the tunnel', 'through the forest', 'through the crowd'. The test: a bridge is a surface (across); a tunnel is a tube you are inside of (through).