What does "гэдгийг" means?
I saw a sentence.
Би үүнийг эзэмшин нисдэг юм гэдгийг түүнд хэлж байхдаа омог бардам байлаа.

What does "гэдгийг" means?
What is base form of гэдгийг? Is it гэдэг?

Question

What does "гэдгийг" means?
I saw a sentence.
Би үүнийг эзэмшин нисдэг юм гэдгийг түүнд хэлж байхдаа омог бардам байлаа.

What does "гэдгийг" means?
What is base form of гэдгийг? Is it гэдэг?

Answer

Yes, гэдэг = гэдгийг. Though in this sentence I would use гэж instead оf гэдгийг. About its meaning - I think I'd better use Japanese again. It's similar to:
 ～という、
～ということを～