10 forms

Form I: (fa3al) فعل
Form II: (fa33al) فعّل
Form III: (faa3al) فاعل
Form IV: ('af3al) أفعل
Form V: (tafa33al) تفعّل
Form VI: (tafaa3al) تفاعل
Form VII: (infa3al) انفعل
Form VIII: (ifta3al) افتعل
Form IX: (if3all) افعلّ
Form X: (istaf3al) استفعل

Form I: (fa3al) فعل
A: Form I is made up of the root letters of the word
B: Most often all three letters are consonants
Katab: he wrote
3alim: he knew
C: sometimes the root word has two consonants and a weak letter
Wa3ad: he promised
Zaar: he visited
7aka: he spoke
D: occasionally the root word will have two weak letters and consonant
wafa: he kept (a promise)

Form II: (fa33al) فعّل
Form II is formed by doubling the middle consunant
1. shows cause ...... 9allam: he taught, caused to know
2. gives intensive meaning ...... kassar: smashed into pieces

Form III: (faa3al) فاعل
Form III is formed by inserting and long alif after first consonant.
And most of this form take direct object but seldom use a preposition.
1. Attempt ...... qaatal: he fought someone
2. shows mutuality of action ...... kaatab: he corresponded (with)

Form IV: ('af3al) أفعل
Form IV is formed by prefixing true hamzi and three concosant.
It is similar to form II in showing cause and is more commonly used in writing.
'arsal: he sent out
'arja3: he returned something

Form V: (tafa33al) تفعّل
This formed by prefixing (ta) to form II.
Ta3allam: he learned

Form VI: (tafaa3al) تفاعل
This formed by prefixing (ta) to form III.
taqaatal: fought each other
some tomes give idea of pretending to be:
tajaahal: he pretended ignorance

Form VII: (infa3al) انفعل
This formed start with (in) and then three consonant, it's common way of communication passive meaning form I.
infatah: was opened

Form VIII: (ifta3al) افتعل
This form prefixing a hamzit wasil to the root and after first consonant add (t).
The meaning as form I
ijtama3: gathered together

Form IX: (if3all) افعلّ
Form IX is formed by prefixing hamzit wasil to the root form and doubling the final letter.
it's used to indicate the changing of color or when referring to bodily defects.
ihmarr: he turned red (he blushed)

Form X: (istaf3al) استفعل
it's start with (ista) and then three consonant.
1. seek for (refers to meaning of the root word)
istaxdam: he employed, used
2. consider to be (relates to meaning of the root)
istahsan: he considered (something) to be good