You would not use 'reason out' as a phrase in a sentence, the juxtaposition of those to words together is not good English.
For the reason stated in my last email, I will not be attending the reunion.
No reason why not...
There was a legitimate reason for him to be upset.
The age of enlightenment is also known as the age of reason.
What is a sentence for this word? I entered the contest for a chance at a prize.
The man's slothfulness is the reason for his attitude towards life.
The reason for the lack of money at the company is overproduction.
The reason why my sexual parts in my body are like this is because of an androgen.
I see no reason for not including the Baltic proviso in this case.
because - when the action have the reason so that - when the action have the the cause
The underlying reason I go to school is to learn and get smarter.
Yes, > I've postdated a bank check for security reason.