Vowels in Arabic are called harakat حَرَكَات, the singular of which is haraka حَرَكَة. Fortunately for the learners of Arabic as a foreign language, vowels in Arabic are simple and limited. They are simple in that they are easily produced which makes the articulation of words straightforward. These vowels are [a], [i], and [u]; and for each short vowel, there is a corresponding long vowel. These are [aa], [ii], and [uu], respectively. So, there are six vowels in Arabic.
(1) Short Vowels:
The short vowels in Arabic are called الحَرَكَاتُ الْقَصِيرَة. They are represented by three diacritical marks placed above or below the consonant that precedes them: the fatha, the kasra, and the dhamma. The fatha (ــَـ) is pronounced as [a]. The kasra (ــِـ) is pronounced as [i]. The dhamma (ــُـ) is pronounced as [u]. Therefore, they are secondary sounds that accompany letters. It worth noting that these vowels are not written in Modern Standard Arabic, but they are fully articulated. Put another way, although seemingly additional, they are considerably essential, for they determine the part of speech of the word, its function, and its meaning. For example, by changing the diacritical mark that accompanies the word علم, multiple words are generated: عَلِمَ ‘he knew’ is an active verb, عُلِمَ ‘was known’ is a passive verb, عِلْم ‘science’ is a noun, عَلَم ‘flag’ is a noun, عَلَّمَ ‘to educate’, among other words. Pedagogically, therefore, it essential that learners of Arabic learn how to add them to words from the outset of their learning.
(a) fatha الْفَتْحــَــة (ــَــ):
As can be seen from its shape, the fatha is a small alif (ا) lain down on the letter (this shape was proposed by the renowned Arab grammarian Al-Khalil ibn Ahmed Al-Farahidi in the 8th century). It is pronounced as [a], that is a reduced alif. At the word-level, it can determine the part of speech of words and may change word-meanings.
He went out
He looked at
(b) kasra الْكَســْــرَة (ــِــ):
Proposed by Al-Farahidi in the 8th century, the kasra is a small alif (ا) laid down below the letter. It is put underneath the letter because it is the opposite of fatha. It is pronounced as [i], that is a reduced yaa. Like the fatha, it can determine the part of the speech of the word and may change word-meanings.
He became happy
He paid a fine
He was sad
He was shy
(c) dhamma الضَّمــَّــة (ــُــ):
The dhamma is a small waaw (و) added above the letter. It is pronounced as [u], that is a reduced waaw. Like the other two diacritical marks, it can determine the part of speech of words, and it may affect word-meanings.
He grew up
He became small
(2) Long Vowels:
Long vowels in Arabic are called الْحَرَكَاتُ الطَّوِيلَة. They are represented by three letters that are saakina (i.e. have a sukuun) over them—the alif, the yaa, and the waaw. The alif (ـا) is pronounced as [aa], the yaa (ـيـ) is pronounced as [ii], and the waaw (ـو) is pronounced as [uu]. In Arabic, these letters are also called weak letters (أَحْرُفُ العِلَّة) or the letters of prolongation (أَحْرُف المَدّ).
(a) The alif ـا :
Pronounced as [aa], the alif ـا is a prolonged fatha, so it is called a long fatha. It is always saakina (i.e. has a sukuun over it), and the letter that precedes it must have a fatha over it. So, given that it is always saakina and must be preceded by a letter that has a fatha over it, it never occurs at the start of words.
(b) The yaa ـيـ :
Pronounced as [ii], the yaa ـيـ is a prolonged kasra, so it is called a long kasra. Like the alif, it is always saakina (i.e. has a sukuun over it), and the letter that precedes it must have a kasra below it. If the yaa occurs at the start of words, it is not a long vowel.
(c) The waaw ـو :
Pronounced as [uu], the waaw ـو is a prolonged dhamma, so it is called a long dhamma. Like the other two long vowels, it is always saakina (i.e. has a sukuun over it), and the letter that precedes it must have a dhamma above it. Given that is it is saakina and the letter preceding it has a dhamma over it, it, as a long vowel, never occurs at the beginning of words.
(3) Short Vowels Vs. Long Vowels:
(1) fatha vs. alif: ــَـ vs ـا
In the following list, the words are minimal pairs (i.e. they differ only in the length of vowel). Besides the changes in pronunciation (from a short vowel to a long vowel), there is a change in meaning.
He became happy
He wrote to
(2) kasra vs. yaa: ــِـ vs. ـيـ
The yaa is basically a long fatha. In the following list, in addition to the change in pronunciation, there is change in meaning.
He was sad
He became affluent
He was safe
He was stingy
(3) dhamma vs. waaw: ــُـ vs. ـو
The prolongation of dhamma results into a letter, that is a waaw which is pronounced as [uu]. This change in the length of sound can have some change in meaning, as in this list.