Japanese phrase
遅れる理由は___です。 oku re ru ri yū wa ___ de su
Meaning
The reason for being late is ___.
When to use it
States why someone will be late. This wording is relatively formal and clearly identifies the cause of a delay.
Example dialogue
どうして遅れるんですか？ dō shi te oku re ru n de su ka
Why will you be late?
遅れる理由は寝坊したからです。 oku re ru ri yū wa ne bō shi ta ka ra de su
The reason for being late is oversleeping.