Unlike English, in Arabic there are three type of vowels; (1) short vowel signs (2) long vowels (3) Diphthongs

(1) vowel signs "Haraka"   also known as short vowels   "a"    "i"   and  "u" which are not part of Arabic alphabet but they  are merely oral, and used only in teaching texts for guiding the learner
(2) vowels letters  long vowels    "aa" "ii"  and "uu" one of their  function is to slightly lengthened the short vowels described in (1) above

(3) Diphthongs Alif and Ya "ay" and Alif and Waw "aw"

In linguistics term, diphthongs are complex speech sound or glide that begins with one vowel and gradually changes to another vowel within the same syllable. 


Fathah  (Zabar) sign;  an oblique dash over a consonant like     represents  "a"  sound

Kasra (Zer) sign;an oblique dash under a consonant like     represents  "i"   sound

Damma (Pesh) sign; a loop over ,resembles like comma, like   represents   "u" sound    


Letter Alif which lengthen the Fathah  (zaber) "aa" 

Letter Ya which lengthen the Kasra (Zer) short vowel "ii" 

Letter Waw which lengthen the Damma (Pesh) short vowel "uu" 

3. Diphthongs