I've had a little idea in mind for a fictional setting, where I wanted to create two dialects of an existing language. Basically, it would be the 'languages' of two opposing factions; in this particular case, good and evil. The dialects are called Elysiani and Tartaran, respectively. The dialects are to be of Ancient Greek, though perhaps a little more separated than normal dialects would be.

Ideally, I would have the two languages to be mutually unintelligible - that is, a speaker of Elysiani would not understand most of what it said by a speaker of Tartaran, and vice versa.

So far, my work is mostly on morphology and lexicon, given my very limited understanding of the Greek language, both ancient and modern. Based on what I've done right now, Elysiani is closer to Modern Greek, and Tartaran is closer to Classical Greek, specifically the Argosian dialect. If anyone could provide ideas and/or insight, that would be wonderful.

(And yes, I know the difference between a dialect and a language. It's perfectly possible for two dialects of the same language to be mutually unintelligible though! )

Theoretically, dialects that are not mutually unitelligible are not the same language, but political mesures can cause it to be considered as the same one.

Apart from that, it's an interesting idea. I think that you could work on phonologycal alterations (as tonic vocalisation as atone one, some consonant alteration...) too. In addition, syntactic changes may be interesting.

Yeah, most dialects are mutually intelligible. There are some cases (Mostly with African languages) where a creole is required for a speaker of each dialect to understand each other, but then again, there's so many languages in that family that it's hard to define where a dialect ends and a language begins.

At the moment, the letters Beta, Eta and Upsilon are pronounced differently in each 'language'; as <b̪>/<v>, <ɛː> and <i> for Elysiani, and <b>, <hɛː> and <aɪ> for Tartaran. There are also many other more subtle phonological differences, mostly with vowels, but they are less consistent and I've yet to define them clearly.

Some words that don't exist in Ancient Greek, obviously, I've had to grab from the modern equivalent, or coin a new word out of existing ones.

As for syntactical changes... Well, my knowledge of Ancient Greek grammar is almost nil. I've yet to plan out any sort of profile for either of the dialects/languages.

I'm evolving a proto language into a modern language, so I should be able to create another modern language from the proto. I guess that's the best way to create dialects. Look at the work of Rosenfelder!

Yeah, I've spent a fair amount of time peering over the articles on his website. It's great stuff, but I find it helps more with making a priori languages than anything else. Making dialects of an existing language, though? Ehh... It's a little hard to figure out how far apart two tongues can be before they are considered completely different languages.

Basically, my idea is that, if you compared Elysiani to Tartaran, they would be considered different languages. But if you compared them to Ancient Greek as well, then they'll look like dialects. Purely a matter of perspective, really. Additionally, I don't know much about any dialects in particular. The closest thing I know is the difference between Castellano and Mexican Spanish, and that's really mostly in the slang and pronunciation. And a tiny, tiny bit of syntax.

I think the things that really make convincing dialects are slight phonological changes, maybe a merger here and there, different vocabulary for some things, and perhaps a slight change in the verb paradigms.

"Mutual intelligibility" is a very ill-defined criterion. It has as much if not more to do with exposure and willingness on the part of the speakers as it does to do with any actual linguistic characteristics.

I think that the vocabulary differences are key. Consider how, for instance, sociolects like youthspeak or legal jargon are virtually impenetrable to outsiders despite the fact that differ only minimally from the standard language in phonology or morphosyntax.

A very clear example of mutual intelligibility that I usually show people is by pointing them to the Scots Wikipedia, given that the language is mutually intelligible (at least in text; most people have a hard time understanding Scots because of the heavy accent) with English.

Colloquialisms are a good idea, though. If anything, I could insert connotations for many words to reflect the strikingly different culture between the two groups. So the same word would probably mean slightly different things, or even completely opposing ideas in some cases.

Actually, it illustrates exactly what I was talking about: with a certain amount of goodwill, English-speakers with an exposure to Scots can understand it. That's why so many Irish scoff at the idea of "Ullans" being treated as a full language on par with Irish Gaelic. But most American English speakers I know can't understand it at all, and struggle just to comprehend Standard English spoken with a heavy Scottish accent.

The funny thing about Scots is that it's estimated that there's a huge number of native speakers out there that don't even realize they're speaking Scots; they think they're speaking really accented English.

But yes, I do agree that mutual intelligibility has a fair degree of uncertainty attached to it. I can understand Scots just fine (and even speak some, to a limited degree); the rest of my family cannot. "What did he say?"

I'm still messing around with the phonology in my dialects. Hopefully I can find some detailed information on Ancient Greek that actually lets me construct coherent sentences with the words I have. Unless someone is willing to help?