In the last grammar post, we talked about conjugating regular verbs in the present and future tense. But, as with every language, not every word is 'regular'. I always used sigh in despair when I heard this 'irregular' word in my studies of other languages in high school, but you need not! Luckily, Arabic is pretty simple regarding all verbs, even the irregular ones and what makes an irregular verb is very easy to remember.
Most irregular verbs occur when one of the root letters of the word is a waw (و) or a yeh (ي) or a hamza (ء). This is because these sounds can mutate into long vowels which makes the pattern of the word change (i.e. a و can sound like -ou- depending on where it is in the word, a ي can sound like -ee- etc.).
There are 3 main types of irregular verbs:
1. Defective verbs - the present stem of the word starts with a long vowel.
i.e. yaakol ياكل - to eat (aakol - present stem)
yaa5od ياخد- to take (aa5od - present stem)
The only thing this irregularity changes is that when you are conjugating the verb (adding the extra letters to make the verb refer to he, she, I, it) then you only add the first letter of the prefix, leaving out the vowel (t-, n- etc.).
So naakol ناخل- we eat. Simple as that!
2. Hollow verbs - there is a long vowel in the middle of the present stem.
yerou7 يروح- to go (present stem - rou7)
yezeed يزيد - to increase (present stem - zeed)
yenaam ينام - to sleep (present stem - naam)
The only difference this type of irregularity makes is that you stress the last syllable of the word after conjugating. Example yerou7. Compare this with, for example, the verb, yenzel ينزل (to alight, to go down).
3. Weak verbs - there is a long vowel at the end of the present stem (see the pattern here?)
yeS7a يصحا - to wake up (present stem - S7a)
yeb2a يبقا- to remain (present stem - b2a)
In a weak verb, we remove the final vowel before adding a prefix. For example:
yes7o يصحو- they wake up
tes7y تصحي - you wake up (to a female)
.. and that's it!