Hi sham, in short answer: Arabic and Arabian are adjectives and Arab is a noun, - Arabic is the language of Arabs or related to the Arab or Arabic - Arabian: a native or inhabitant of Arabia, related to the nationality o the place s/he came from,: - he's Arabian, he's from Yemen - he's Arabic, he's from a country in which they speak Arabic - Arab here is a noun, means an inhabitant of the Arabia, or a horse originated from this area

I would say "He is an Arab" or "He is Arab". "Arabic" is usually used to refer to the Arab language. "Arabian" is correct and can be used instead of "Arab", but it "Arab" would be far more used. "He is an Arab man" is redundant, because "he" already tells us the person you are talking about is a male.

Arabic: is the language or anything related to it. Arab: A totalitarian political-linguistic word refers to any person from any Arabic-speaking country and speaks Arabic as mother-tongue plus not being of a specific standing ethnicity or group like: Kurds, Turks, Armenians, Amazigh...etc. (since Middle East is very diverse specially The Mediterranean countries) Arabian: A racial term refers to any person who is originally (ethnically) from Arabian peninsula (Natives of the present Gulf countries). Also refered to as "Native Arab".