Meaning of MIDDLE in English
BAD : The girl was of middle height and was wearing a blue suit.
GOOD : The girl was of medium height and was wearing a blue suit.
When you are talking about someone's height, weight, etc, use medium (NOT middle ): 'The man that police wish to question is of medium height and has a small black moustache.'
BAD : The wallet was middle brown and contained sixty dollars.
GOOD : The wallet was medium brown and contained sixty dollars.
When you describe the colour of something, use medium (NOT middle ): 'a medium grey suit' (= neither light grey nor dark grey but somewhere in between).
BAD : On the middle of September she is going on maternity leave.
GOOD : In the middle of September she is going on maternity leave.
in the middle of (NOT on ): 'The cat dropped the mouse right in the middle of the kitchen floor.' 'What do we do if the fire alarm starts ringing in the middle of an examination?'
Longman Common Errors English vocabulary. Английский словарь распространенных ошибок Longman. 2012