Arab (pronounced ARR-ub) is the adjective used in relation to the race, culture and politics of the people known as the Arabs:
Arab countries, Arab culture, the Arab League, etc.
Arabic (pronounced ARR-a-bik) is the name of the language spoken in Arab countries. The language of the Koran is Classical Arabic; modern varieties are referred to as Egyptian Arabic, Syrian Arabic, etc. As an adjective, Arabic generally means ‘written in, or some way related to the Arabic language’, as in:
an Arabic inscription, Arabic numerals, Arabic script, Arabic poetry, etc.
Arabian (pronounced a-RAY-bee-un) generally refers to the geographical region known as Arabia, as in:
the Arabian peninsula, the Arabian deserts, Saudi-Arabian politics, Arabian oil wells, Arabian horse
It is also found in the title of the famous collection of stories, also known as A Thousand and One Nights:
The Arabian Nights
Note that Arab, Arabic and Arabian are all written with a capital letter.
To sum up: Arab relates to people, Arabic refers to language and Arabian is used in connection with land.
©2014 Baxter Publishing, Hilversum, The Netherlands