I'm a little tired todayI do not know what is the reason
1) I'm a little tired today
I do not know what is the reason ...

2) I'm little tired the day
I am not aware what is the reason ....

هل الجملة الأولى اصح ام الثانية ؟

Question

I'm a little tired todayI do not know what is the reason
1) I'm a little tired today
I do not know what is the reason ...

2) I'm little tired the day 
I am not aware what is the reason ....

هل الجملة الأولى اصح ام الثانية ؟

Answer

More natural:
1) I'm a little tired today
I don't know why.

Answer

I'm A little tired today.
I do not know what the reason IS.

Answer

I'm a little tired today.

I do not know why.
I do not know the reason.
I do not know the reason why.
I do not know what the reason is.
I do not know what the reason why is. [this doesn't sound too good]

"aware" is better when you are told information from someone else. It is probably due to something you did or didn't do.

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