[nihzm]

A tangentially related interesting note is that in German zwo also meant two, and so did zween. In old German some numbers were gendered and zwo is the feminine form. The only form that is used today "zwei" is the netuer form. Some languages still have this feature, for example in Russian "two" are два (m+n) and две (f). So this change is (technically) grammatically correct. English also had something similar (cf. twain).

[dkarl]

Zwo is still common today, because it's the word for two in some German dialects. The military adopting zwo would be similar to the American military adopting "y'all," a word that's commonly used and universally understood.

[nihzm]

You're right, in southern Germany, Switzerland and Austria (?) it is still widely used in everyday life. It's interesting how northern dialects "choose" zwei while the southern ones preferred zwo. Also, IIRC in some regions the (few) elderly still use all three with their original grammatical rules.

[lxgr]

It's definitely not common in Austria, and I also haven't heard it in Germany (outside of a "clarity of communications" context on the phone). Bavarian (which is close to many Austrian German variants) would use "zwoa", which sounds quite different too.

[fnordian_slip]

In Franconia, we use "zwo", "zwä" and "zwei", but it might just be very local to the small towns in my area.

[xen0]

As a non-native speaker, I've used it a couple of times at a bakery to make sure I don't get too much of what I'm asking for.

Doesn't help when I _do_ want three of something though...

[ithkuil]

In Croatian (and possibly other related languages) the number two (dva), like one (jedan), declines according to gender and case

Jedan prozor, jedna jabuka Dva prozora, dvije jabuke

Another unrelated quirk in Croatian (and I don't which other related language) is that with numbers 2, 3, 4 you use the genitive singular and with higher numbers the genitive plural

Tri prozora, tri jabuke, tri kune Četri prozora, četri jabuka, četri kune Pet prozora, pet jabuka, pet kuna (notice the -a ending)

I learned that when I wrote some software that converted numeric values in textual form. I never noticed the rule despite speaking correctly (born in a croatian family but I didn't attend school there so I only picked up the language by listening family members, reading tv subtitles and books).

I wonder if an average Croatian is aware of that plural forming rule or they just do the right thing without noticing.

[nihzm]

Slavic languages in general seem to have retained this case and gender dependent declination of numbers, making them rather difficult to learn. For example most languages on this list [1] have complex declension tables for the number two.

https://en.wiktionary.org/wiki/%D0%B4%D0%B2%D0%B0

[ithkuil]

But it only works for numbers 1 and 2 and goes away for bigger numbers.

Probably a remnant of the dual case of Proto Indo European

[phyrex]

I’m German and I never knew this! Thanks!