Yes, I agree with Ghabi, it may not be so much a matter learning the awzaan or the numbers, since knowing that a verb is of the form IV / أَفْعَل، يُفْعِل pattern may not be of much help if you are only used to conjugating verbs with sound letters (حروف صحيحة), such as
أَعْرَبَ، يُعْرِبُ. In the case of verbs that have defective lettrers (حروف علة), such as
أَيْقَنَ، يُوْقِنُ, you would also need to know rules of إعلال. In the case of
أَيْقَنَ، يُوْقِنُ you would need to know that تُقلَب الياء واوًا إذا سُكِّنَت بعد ضمة (
yaa2 is converted to a waaw if it (the yaa2) has a sukuun over it after a Damma). So that means that the regular (perhaps intuitive) conjuagtion of
يُيْقِنُ becomes
يُوْقِنُ because the combination ي
ـــُـيــْــقن (Damma, yaa2, sukuun) is not allowed (probably due to the difficulty that would create in pronunciation).
At any rate, to answer Timmy's question:
May I ask how you learn them? Is it just as you go along naturally so to speak?
The best way to learn it is to just memorize the conjugational pattern of أَفْعَل، يُفْعِل / form IV verbs that have a defective first root letter (either waaw or yaa2). what you could do is just replace the ف in
أَفْعَل، يُفْعِل with either و or ي depending on what the first root letter is, like this:
If the first root letter is و, then:
أَوْعَلَ، يُوعِلُ
And if the first root letter is ي, then:
أَيْعَلَ، يُوعِلُ
Or better yet (as the above may seem a bit strange), just use two real verbs as your "go-to verbs," so to speak, to help you remember the pattern, such as
أَوْقَف، يُوقِفُ (to stop) for waaw and
أَيْقَنَ، يُوْقِنُ (to be certain) for yaa2. And then, for example, when you see another verb such as أيسر you will know that it is conjugated like
أَيْقَنَ.
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As far as the numbers vs. awzaan thing, I like both. I imagine the number system arose to act as kind of a shortcut in lieu of saying out the entire pattern. This may helpful for those (non-natives) who may have difficulty is pronouncing or aurally recognizing the patterns (when they first start out learning) or it may just be a way to categorize the verb patterns. This may also be useful to the linguist who is only interested in a theoretical understanding of Arabic, but who does not want to learn the language. For the untrained ear it can be difficult to perceive the difference between فَعَلَ (fa3ala) and فَعَّلَ (fa33ala), let alone pronouncing the 3ayn. So in this sense, it may make sense to refer to them in a different way as a shortcut, such as using form I and form II. Perhaps the creation of the number system was unnecessary, but so what. I think that there is room for new/different ways of thinking about about things. Thinking about something in a different way may also help us to understand it better or understand it in a different way. I think we also must bear in mind that different peoples organize and process information in different ways. Perhaps those who came up with the number system thought it was easier to assign numbers to the different conjugations and categorize them that way. Who knows. The point is, new ideas about old things that may seem superfluous or unnecessary are not necessarily bad.