Arabic uses a cursive alphabet, with letters taking different forms at the beginning, middle and end of a word. These letters have a fundamentally different basic shape than Latin-based alphabets, so learning the alphabet is not like learning the letters of another Latin-based language. Additionally, students will have to learn the combinations of letters that take a form outside of the normal rules, and the vowel system that is only fully written on formal texts.
Arabic has a few letters with sounds that are slightly different than each other. While children who grew up speaking Arabic have been attuned to this difference since childhood, those seeking to learn it as a second language can have difficulty distinguishing among the two sounds. These include two letters with the basic sound of the letter "d," with one slightly more deeper than the other, and two letters with a basic "th" sound, but one higher and one lower in tone.
While it is adorable when small children try to figure out how to make the sounds of a given language, adults are frequently reticent to put on such a spectacle. This is a major obstacle when learning to pronounce a few of the letters that require different throat actions than any English sound. For example, learners must learn how to make a guttural rolling sound both high in the throat and low in the throat.
A final aspect of Arabic that confounds both those students for whom Arabic is a first language and those for whom it is a second language is identifying the purpose each word serves in a sentence, according to Arabic's complex system of grammar, and adding the appropriate vowel sound. This exercise requires the student to draw on everything he knows about Arabic grammar, and draw connections between several different words that could all potentially serve several different purposes.