A preposition is a word that tells you where or when something is in relation to something else. Examples of prepositions include words like 'after', 'before', 'on', 'under', 'inside' and 'outside'.

but there is space here only for a few of them. If you are in doubt as to which preposition to use, always check with a good dictionary.

The interchangeable use of ‘in’ and ‘on’ is inadmissible. It helps to remember the various types of prepositions to avoid their misuse. There are time prepositions (before, after ...