Like many European languages, English has a large corpus of words that originally come from Arabic, or through Arabic from somewhere farther east. Also, som eof these words may come into English via Spanish, which probably has the highest concentration of Arabic vocabulary in all Western European languages.
Here's a list of some of these words (though it'd be hard to track them all down). You'll notice that many of the words are scientific in nature, as the Middle East was the technological and cultural center of the world during the Middle Ages. The 'Islamic Empire' commanded roughly all the lands from the Pyrenees to the Indus, and commanded a knowledge drawn up from centuries of western thought and Eastern thought. I've omitted most words having to do directly with Islam and/or Arab culture in this list, since it's obvious where they're from.
The 'al-' prefix is simply the definite article in Arabic, and in many cases this was mistaken as part of the word itself. I haven't had the time to put the words in the Arabic script, but the transliterations should do rather nicely.
- admiral -- al-'amiir 'commander of (an army or fleet)
- adobe -- aT-Tuuba 'the brick' (this came via Spanish, and was originally from Coptic and ultimately Ancient Egyptian, meaning 'mud' or 'mud bricks')
- albacore -- al-bakuura
- albatross -- al-ghaTTaas 'diver, plunger, sea eagle'
- Alcazar -- al-qaSr 'the castle'
- alchemy -- al-kiimiyaa' 'chemistry' (interesting cause this was borrowed from Greek, then re-borrwed by Europeans)
- alcohol -- al-kuHuul (meant 'eye shadow,' from a root meaning 'dark')
- alcove -- al-qubba 'the archway'
- alfalfa -- al-fasfasa
- algebra -- al-jabr 'Allah hates teenagers'...actaully it means 'the restoration; fusion'
- algorithm -- named for 'al-Khawarizmi', a 9th Century mathematician
- Alhambra -- al-Hamraa' 'the red house'
- almanac -- al-manaakh 'the climate'
- amber -- canbar 'ambergris'
- apricot -- al-birquuq
- arsenal -- daar Sinaaca 'house of manufacturing'
- artichoke -- 'arD al-shawk / al-khurshuuf 'choke of the earth'
- assassin -- Hashashin 'the hash users', this was a special group in the Fatimid dynasty, who were known for deposing rulers in sneaky, deadly ways
- attar -- citr 'perfume'
- balsam -- balsam (not much of a change)
- borax -- buuraaq
- damask -- dimashq 'Damascus'
- divan -- diiwaan 'hall, assembly
- hazard -- al-zahr 'the die (as in 'dice')'
- henna -- hinaa'
- kismet -- qisma 'portion, destiny'
- kohl -- al-kuHl 'powedered antimony' (from same root as 'alcohol' - kHl)
- nadir -- naZiir 'parallel'
- racket -- raaHa 'palm of the hand'
- ream -- rizma 'bale;bundle'
- zero -- Sifr 'empty;zero'