Is it correct to say proficient knowledge?

While "proficient knowledge" is grammatically correct, it's a bit redundant.

Here's why:

* Proficient already implies knowledge. Being proficient in something means you have a high level of skill and understanding.

* Knowledge refers to information or understanding.

Instead of saying "proficient knowledge," you could use:

* Proficiency

* Strong understanding

* Extensive knowledge

* Deep understanding

For example:

* Instead of: "He has proficient knowledge of Spanish."

* You could say: "He is proficient in Spanish." or "He has a strong understanding of Spanish."

Using a more specific and concise term will make your writing clearer and more impactful.