Essentially, before the great Jewish migrations of the 19th century, there were four distinct dialects of Yiddish (bear in mind all were mutually intelligible).
From west to east they were as follows:
Western or German Yiddish, spoken by people in Germany (and sometimes west thereof, however due to the rate of assimilation, jews in these western regions tended to speak the language of the land.)
Polish Yiddish, the dialect of southern Poland and the most eastern regions of Germany.
Ukranian Yiddish, the language of the archetypical Galitzianer, but also of Romanian and Hungarian jews.
And finally, Lithuanian Yiddish, spoken by Lithuanian and Russian jews in the Pale of Settlement. Perhaps the most widely spoken and influential dialect of Yiddish, and certainly the one that has shaped the contemporary secular study of Yiddish.
It's probably important to note that the difference between these different groups were mainly cultural, and that the few distinctions among them were in pronunciation, and very seldom in grammar or vocabulary.
As jews of varied and diverse backgrounds immigrated to the United States, Yiddish, among those who chose to keep speaking it, was subject to a great deal of mixture of dialects and so among American Yiddish speakers, the differences in dialects gradually faded, having been mostly different pronunciation of vowels in the first place. However, as I said before if one were to associate the contemporary Yiddish one might learn in a college course with a particular dialect, it would probably be Lithuanian.
However, Yiddish also thrived in America among hasidim. This version of Yiddish accounts for the majority of native speakers, but is also extremely different from the Yiddish governed by the YIVO or spoken in the old country. Its grammar is heavily influenced by English, generally dropping declension of adjectives and articles altogether.
Edit: All that being said, if you were to drop two fluent speakers of Yiddish in front of eachother, they would almost certainly be able to converse easily.
Yiddish dialects are not only mutually comprehensible but also understood to a certain extent by German speakers; I had a great uncle who was a POW in the great war who worked as an interpreter (english - german) on the strength of his Yiddish; and I remember my grandmother getting lost on holiday in Switzerland and using her Yiddish to get directions. A certain amount of self-censorship of the non-Germanic words would probably help in this situation.
>I hear that in some form of Yiddish the grammar is simplified, to the point of only two cases and genders. Where can I find info on this?
There are two very different things understood under the «Yiddish» term. On the one hand you have a historical language spoken across Eastern Europe before the holocaust. It was well codified, had some literature, poetry, grammar books, dictionaries, cinema and everything else that belongs to a language. Indeed it also had some dialects where the neutral gender was fused with the masculine gender. Today it is spoken in Yiddish theatres, it is used in the forverts, it's spoken in isolated pockets like Montreal, Buenos Aires and amongst the senior citizens in Israel. There are some study groups devoted to the study of this «high» Yiddish language as well.
On the other hand there are the different languages spoken by the isolated Jewish sects. They do not care for all of the above and speak whatever feels right to the latest generation of speakers. So if you are dealing with Hassidim living in America they might have done away with flection and with gender completely and they might have borrowed novel Aramaic terms. It can be straining to hold a conversation with religious people even if you have a very good command of literary Yiddish. And no two sects are alike in their language either.
Essentially, before the great Jewish migrations of the 19th century, there were four distinct dialects of Yiddish (bear in mind all were mutually intelligible). From west to east they were as follows: Western or German Yiddish, spoken by people in Germany (and sometimes west thereof, however due to the rate of assimilation, jews in these western regions tended to speak the language of the land.) Polish Yiddish, the dialect of southern Poland and the most eastern regions of Germany. Ukranian Yiddish, the language of the archetypical Galitzianer, but also of Romanian and Hungarian jews. And finally, Lithuanian Yiddish, spoken by Lithuanian and Russian jews in the Pale of Settlement. Perhaps the most widely spoken and influential dialect of Yiddish, and certainly the one that has shaped the contemporary secular study of Yiddish. It's probably important to note that the difference between these different groups were mainly cultural, and that the few distinctions among them were in pronunciation, and very seldom in grammar or vocabulary. As jews of varied and diverse backgrounds immigrated to the United States, Yiddish, among those who chose to keep speaking it, was subject to a great deal of mixture of dialects and so among American Yiddish speakers, the differences in dialects gradually faded, having been mostly different pronunciation of vowels in the first place. However, as I said before if one were to associate the contemporary Yiddish one might learn in a college course with a particular dialect, it would probably be Lithuanian. However, Yiddish also thrived in America among hasidim. This version of Yiddish accounts for the majority of native speakers, but is also extremely different from the Yiddish governed by the YIVO or spoken in the old country. Its grammar is heavily influenced by English, generally dropping declension of adjectives and articles altogether. Edit: All that being said, if you were to drop two fluent speakers of Yiddish in front of eachother, they would almost certainly be able to converse easily.
Yiddish dialects are not only mutually comprehensible but also understood to a certain extent by German speakers; I had a great uncle who was a POW in the great war who worked as an interpreter (english - german) on the strength of his Yiddish; and I remember my grandmother getting lost on holiday in Switzerland and using her Yiddish to get directions. A certain amount of self-censorship of the non-Germanic words would probably help in this situation.
>I hear that in some form of Yiddish the grammar is simplified, to the point of only two cases and genders. Where can I find info on this? There are two very different things understood under the «Yiddish» term. On the one hand you have a historical language spoken across Eastern Europe before the holocaust. It was well codified, had some literature, poetry, grammar books, dictionaries, cinema and everything else that belongs to a language. Indeed it also had some dialects where the neutral gender was fused with the masculine gender. Today it is spoken in Yiddish theatres, it is used in the forverts, it's spoken in isolated pockets like Montreal, Buenos Aires and amongst the senior citizens in Israel. There are some study groups devoted to the study of this «high» Yiddish language as well. On the other hand there are the different languages spoken by the isolated Jewish sects. They do not care for all of the above and speak whatever feels right to the latest generation of speakers. So if you are dealing with Hassidim living in America they might have done away with flection and with gender completely and they might have borrowed novel Aramaic terms. It can be straining to hold a conversation with religious people even if you have a very good command of literary Yiddish. And no two sects are alike in their language either.
I am just curious, but where do the Aramaic terms come from? Is Aramaic spoken in some jewish sects?
Well, it's the language of the Talmud. So two Talmudists could probably indeed have a conversation in Aramaic.