معرفة ma'arifa is knowledge in Arabic..
Arabic does not use infinitives. Verbforms are refered to under the perfect form of the 3rd person singular. عرف - arafa he knew
We have had that discussion in class - in semitic languages it is often said there is no infinitive like in, say German or English, but do these two not "simply" use the first person plural in/for the infinitive? :) (+ see below - you can make an infinitive form from it :))
But Akkadian and hebrew have infinitives - Akk. paraasum, Heb. lifros (li ="to", pros <paros <*paraas). You can't say there is no infinitive in semitic languages.
No, (as in English) it follows class 6 (ji/ma-) agreement, and is a loanword from Arabic.