noun
BAD : She was sitting on her favourite armchair.
GOOD : She was sitting in her favourite armchair.
◆◆◆
sit (down) in an armchair (NOT on ): 'He sat down in the armchair and almost immediately fell asleep.'
noun
BAD : She was sitting on her favourite armchair.
GOOD : She was sitting in her favourite armchair.
◆◆◆
sit (down) in an armchair (NOT on ): 'He sat down in the armchair and almost immediately fell asleep.'
Longman Common Errors English vocabulary. Английский словарь распространенных ошибок Longman. 2012