Grammar fix
main reason
most important reason
The biggest or most important reason for something happening or for a decision.
collocationB1common
Hear it in context
Notice where the phrase sounds natural.
- The main reason I moved to this city was for a better job.daily life
- The main reason I prefer public transport is because it’s more convenient and better for the environment.IELTS speaking
Fix the pattern
Pattern: the main reason (for something) is/was...
WrongThe main reason of leaving was the pay.
RightThe main reason for leaving was the pay.
'Main reason FOR' something — not 'of'.
Patternthe main reason (for something) is/was...
Use it right
Choose the version that sounds natural in speech.
'Main reason' is the plain everyday phrase; 'principal motivation' is essay-formal.
Build natural chunks
Words that usually travel with it.
the main reason + for/whyforwhybehindis that
Don't confuse it
‘Main reason’ is stronger and clearer than just ‘a reason’ or ‘an important reason’.