Deciding/determining factor (=the thing that finally makes something happens)
Race should never be a deciding factor in a hiring decision.
Reason "Why are you helping her?" "She asked me to. That's the only reason."
The main reason she quit is that she was not being paid enough.
Reason for/behind Can anyone explain the reason for the delay?
There were two reasons behind the company's failure.
Reason why/ (that) The reason why the economy is growing more slowly is a lack of workers.
Reason to do something There's no reason to doubt what she says.
Origins of The origins of the crisis were very complex.
Other cultures' beliefs about the origins of disease often differ from our own.
Have origins in Many of our attitudes to the issue of race have their origins in the colonialism of days gone
by.
Root of The roots of the wars in the Balkans go back hundreds of years.