how should I understand ?
"Reading is of vital importance in language learning" Here "of", How should I understand?
if I write like this "Reading is vital importance in language learning" can I?

Question

how should I understand ?
"Reading is of vital importance in language learning"      Here "of", How should I understand?
if I write like this "Reading is vital importance in language learning"  can I?

Answer

You need the "of".
"vital importance" is a noun, so you need must use "of".