Japanese phrase
___が主な理由です。 ___ ga omo na ri yū de su
Meaning
___ is the main reason.
When to use it
Presents one factor as the most important cause.
Example dialogue
遅れた理由は何ですか？ oku re ta ri yū wa nan de su ka
Why were you late?
雨が主な理由です。 ame ga omo na ri yū de su
The rain was the main reason.