Confusable Words “until” and “by”

‘Until’ and ‘by’ are often confused.

‘By’ is for a deadline: ‘Please complete this by Friday’ is correct. Don’t use ‘until’ here.

‘Until’ is used for continuing an action: ‘Please speak only English until the end of the class.’
More examples:
‘I studied until 11pm.’
‘The movie had started by the time I arrived.’
‘I lived in Tokyo until 2007.’
‘I have to arrive by 4 O’clock.

‘Until’ is also used in negatives:
“Don’t start until I am ready.”
“I won’t know the result until tomorrow.”