A preposition is a word used before a noun or pronoun to show a place, position, time or method.
Errors in the use of prepositions may not cause misunderstanding but they give an appearance of imperfect or careless learning.
Let's consider some prepositions wrongly used.
Wrong: he stood at the middle of the room.
Right: he stood in the middle of the room.
Wrong: we must be at the alert; lions are in the neighbourhood.
Right: we must be on the alert; lions are in the neighbourhood.
Wrong: she is a well known figure at the international scene.
Right: she is a well known figure on the international scene.
In contrast to 'on the international scene' there is 'at the international level'.
Wrong: Jacob was already on bed when I called.
Right: Jacob was already in bed when I called.
'in bed' is the correct expression even when someone is lying on top of any sheets or blankets, rather than inside or underneath them. But 'on' is correct if a determiner comes before 'bed' and the person is not under the sheets or blankets.
Jacob was sitting on his bed reading a book.
Wrong: I told Chima to come by 3 o'clock. I was surprised to see him at 2.45
Right: I told Chima to come at 3 o' clock. I was surprised to see him at 2.45
'by' when used with a stated time does not mean 'at' or 'on' the stroke of, it means 'any time up to and including, but not later than .....'. In the wrong example, if Chima came by 2.45 that is before 3 o'clock, there was no cause for surprise.
misunderstanding can clearly result from this misuse of 'by'.
Phew, dear lovelies, today I woke up