Reason
Motive, Excuse
noun
A reason reason is a reason! How could it not? Do you have a reason why it shouldn't be? I thought not.
This word means "reason" as in the reason you're studying Japanese, or the reason you're late. That's why it can also mean similar words like motive and excuse.
りゆう
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
とくに理由はありません。
I don’t have any specific reason.
未だけいひのせいさんをしてないのには、何か理由があるんですか？
Do you have any reason for not having settled your business expenses yet?
論理的な理由から、彼は行方不明になったゴム手袋の事件の犯人が風船屋であることを導いた。
For logical reasons, he was led to believe that the culprit in the case of the missing rubber gloves was the balloonist.