How different are Egyptian and Algerian Arabic, really?

Recently, The Economist decided to introduce its readers to the extent of variation across Arabic, by comparing Algerian and Egyptian retellings of a Juha story from Reddit (via LL). Most Arab commenters felt that the post exaggerated the differences, since the stories were being retold in individuals' own words, not translated per se. So let’s try and figure out part of the question this raises here: To what extent can an Algerian understand the Egyptian version of this story, and to what extent does this ability stem from: a) his knowledge of his own dialect; b) his knowledge of Fusha (Standard Arabic); and c) his experience watching Egyptians on TV?

This is the Egyptian quote, in their own transcription (3 = ʕ, 7 = ħ, 2 = ’ [ʔ], 9 = ’ < q; listen):

fi youm min el ayem, kan go7a we'bno bey7addaro 7aget-hom 3ashan yeroo7o el balad elli gambohom. farekbo el etnein 7omarhom 3ashan yabtedo yesafro. we 3a'sekka marro 3ala balad soghayyara keddaho. ba7ala2o el nas feehom we 2alo:  ayoh! bo99o el nas el 2asya elli mabter7amshi rakbeen kollohom 3ala el 7omar.

The first obvious hurdle is pronunciation: an Algerian listener needs to convert Egyptian g back to j, Egyptian ’ back to q / g, and drop most of the short vowels. School won’t help with that – but most Algerians already know this much from watching Egyptians on TV, and even if they didn’t, it shouldn’t take too long to catch on.

What about vocabulary? Well, the good news is that only nine words in this passage are completely absent from Algerian Arabic. The bad news is that six of them won’t be familiar from Fusha either – and that that amounts to something like 15% of the passage.

• b- in b-iħaḍḍaru “they prepare”, marking, loosely speaking, the present tense, has no Algerian equivalent, and no Fusha equivalent either. It is very common in the Middle East, though, so most Algerians will have encountered it on TV; we may not know exactly what it does, but we know to ignore it!
• ʕašān “in order to” corresponds to Algerian bāš. Knowing Fusha won’t help much with this one; its Fusha root, ʕalā ša’n, means “on the affair of”. However, the form is so common in Middle Eastern broadcasts that most Algerians probably know it.
• yibtadu “they start” corresponds to Algerian yəbdāw; both forms derive from the same root, but Algerian Arabic has lost the derived form with infixed -t-, which is also used in Fusha.
• sikka “road” corresponds to Algerian ṭrīq. Both forms are used in Fusha, so a knowledge of Fusha will help here; even a lightly educated Algerian would probably recall as-sikka al-ħadīdiyya, the Fusha word for “railroad”.
• marru “they passed” corresponds to Algerian jāzu. marra is preferred in Fusha in this sense, and would be familiar to any moderately educated Algerian.
• kidahu: I couldn’t even guess what this meant, so I looked it up in my Egyptian Arabic dictionary... apparently it’s the same as kida “thus, like this”, which in Algerian would be hākđa, corresponding to Fusha (hā)kađā. The word itself is thus reasonably easy to identify. But I don’t understand why it’s being used here.
• baħla’u: I assume from context that this means “stare” or something. Let me check... yes, it’s glossed as “to stare, be goggle-eyed”, so Algerian xuẓṛu. I can’t think of any Fusha form that would help you guess this.
• ayyūh: I assumed from context that this was for expressing disgust, but my dictionary says it indicates “forceful intent” (and that it comes from Coptic). Either way, Algerians don’t say this; the best equivalent in context is probably the exclamation of disgust yəxxa. It’s not in Fusha either.
• bu’’u buṣṣu “look” (I think) corresponds to Algerian Arabic šūfu. This word has no commonly used Fusha counterpart, so again a knowledge of Fusha won’t help.

So an Algerian can understand something like 85% of this passage just by figuring out sound changes, and probably more from context – so far, so good!

However, even if we convert the sound system and substitute these eight words, the result will still not be acceptable Algerian Arabic – it violates the language's rules. Most Algerians will tell you that Algerian Arabic has no rules, but that won’t stop them from looking at you funny if you try saying something like:

*f-yūm məl-l-əyyām, kān jħa w-əbn-u yħəđ̣đ̣ṛu ħājəthum bāš yṛūħū l-əl-blād əlli jənbhum, fā rəkbu l-əθnīn ħmāṛhum bāš yəbdāw ysāfru. u ʕla ṭṭriq, jāzu ʕlā blād ṣɣiṛa hākđa, xǔẓṛu n-nās fīhum u qālu: yəxxa! šūfu ənnās əlgāsya əlli mātəṛħəmši rākbīn kullhum ʕla lħmār.

The reason this doesn’t work is because there are a lot of other less obvious differences between Algerian and Egyptian Arabic. The most clear-cut are:

• yōm: Algerians only use yum in əlyum “today” and in counting (xəms-iyyam); for other purposes, “day” is nhāṛ (“days”: nhāṛāt). You can’t say “f-yūm məl-l-əyyām”; the best equivalent would probably be wāħəd ən-nhāṛ (one day).
• ibn-u: (Most) Algerians don’t use bən as an independent word; they only use it in compounds with the meaning “son of...”. In a context like this, you would have to say u-wlīd-u.
• balad: In Algerian Arabic, blād is either broader than “village” (“country, region”) or more specific (“hometown”). A village is dəšṛa or duwwāṛ (or, let’s face it, vīlāž.)
• ħagit-hum: While ħāja means “thing” in Algerian, as in Egyptian, Algerians don’t normally use it to mean “baggage”. The Algerian equivalent would be dūzān-hum.
• ganbu-hum: In Algeria, this would mean literally “their side”. “Next to them” would be ħdā-hum or quddām-hum, depending on the region.
• l-itnēn: In Algeria, this would be interpreted as “Monday”. “Both of them” is fī-zūj; θnīn is used as a number only in compounds, like “thirty-two” (θnīn u θlāθīn).
• ’āsiya: While gāsi does mean “hard” in Algerian Arabic, you wouldn’t use it in the metaphorical sense of “cruel” as here. The feminine singular agreement with “people” would also be odd in much of Algeria, but some do use it.

So even an uneducated Egyptian could more or less make himself understood in Algeria (depending on how sharp the person he's speaking to is and how many Egyptian films they've watched), but to actually speak Algerian, he'd need to do a lot of learning and relearning. It's up to you to decide whether that makes them two quite similar languages or two very different dialects...