Arabic is a funky language, as well as being very old. And it is very different to
Indo-European languages. For one thing, almost all
verbs have exactly three letters in their base form. The base form by convention in
Arabic is actually the
past tense third person. All other forms of the verb are variations on the base form; made by inserting specific letters in any of the four possible places: before the first, between first and second, between second and third and after the third. The
verbs that don't have three letters tend to be the ones that came in from other
languages.
One more cool thing: the verb for "to do" is also three letters long, being fa,ain and lam. So in grammatical textbooks, the first letter of a verb is called "fa" the second is called "ain" and the last letter is called "lam". So it's a big self-referential mess.