Grammatically, Yiddish is almost entirely Germanic - very close to an older form of High German.
In vocabulary, it is mostly Germanic, but with a large admixture of Hebrew words and (depending on the dialect) also significant borrowings from other languages, such as Polish and Russian.
As such, it is not what most scholars describe as a creole:
that is a language whose grammar has arisen spontaneously, generally when a cohort of children grow up among people who communicate in a pidgin (a contact language with little or no consistent grammar).
It appears that given such an environment, small children will mould it into a language with its own grammar, generally bearing little resemblance to that of the language(s) from which the words come.
(This is somewhat controversial, as is the claim that creoles round the world tend to have rather similar grammars).
So with that definition, Yiddish is not a creole
: it is a distinct Germanic language, quite close to German, but which has a large admixture of Hebrew and other words.
english.stackexchange.com/users/547/Colin Fine
A creole language is not necessarily a combination of two languages.
It's just a pidgin language that has native speakers.
A pidgin language is usually a limited, easy-to-learn language used for communications between two different language groups.
Normally it has much simpler vocabulary and grammar.
The hallmark of a pidgin language is that nobody speaks it as their primary language...
it serves as a lingua
franca (shared language) between two linguistic communities.
Pidgins are not necessarily anyone's primary language.
These days people often use basic English as a pidgin even when neither of them is really an English speaker (for example, a Tagalog-speaking sailor might use basic/pidgin English to communicate with an Arabic-speaking merchant when in port, or a Russian tourist in Japan might use basic English to communicate with her hosts).
Sometimes pidgins are used so much that they become primary languages, and kids grow up speaking only the pidgin language.
At that point the language is considered a creole language.
The classic example of this is Haitian Creole, which started out as a simplified version of French used by African language speakers in Haiti, and soon became the primary language kids learned.
Another major example is Tok Pisin in Papua New Guinea.
Yiddish is none of the above, really.
It is mostly an in-group dialect that became a full fledged language when it got its first army ( Joke! )
It was not intended to be used as a lingua franca, although sometimes it served this purpose when Jews from different linguistic communities (e.g. Germany and Poland) used it as a common language.
english.stackexchange.com/users/133/Joel Spolsky
Yiddish is typically referred to as a Creoloid, much like Afrikaans, Michif, and even African American Vernacular English.
That is, they share a lot of common traits with Creoles and Creole Genesis.
Labeling something a Creole or not is debatable
even amongst scholars as many have conflicting views on what makes something a creole.
Try reading either of these for some info on it and judge for yourself.
Jacobs, Neil G. (2005).
Yiddish: A Linguistic Introduction.
Cambridge University Press.
(Scott: PJ 5116.J33 2004); Prince, Ellen (2001).
Yiddish as a contact language.
In Norval Smith and Tonjes Veenstra (eds.), Creolization and contact
english.stackexchange.com/users/2586/asd
Yiddish is called a FUSION language by linguists,(as is English) derived from old High German, beginning around the year 1000in the Rhine Valley.
It contains about 85% German vocabulary, about 10% Hebrew and Aramaic words and about 5% Romance or Slavic words, depending where it was spoken.
Scholars contend that there were/are 4 major dialects - but with overlaps.
What many don't know is that a "stage Yiddish" was created by Abraham Goldfadn (father of the Yiddish Theatre) that blended the various dialects, so that there would be linguistic consistency in performances.
Those whose exposure to Yiddish was mostly through Yiddish theatre and recorded song, have naturally but erroneously came to believe that this "stage Yiddish" was "true" Yiddish, but it was a construct, blending all the various dialects.
english.stackexchange.com/users/2598/Dybbuk Jones
I found an interesting information about this language (I also have a personal interest in the language as both my grandparents still speak it) here: http://www.sefarad.org/hosted/english/eblul/yiddish.html .
Yiddish, which is written in Hebrew characters, is a composite language stemming from Judeo-German, that is to say the languages used by the Jews who settled in the Rhine Valley in the Middle Ages.
Their vernacular language, based on the local Germanic dialect, has been enriched by numerous contributions from Hebrew and from the Romance languages.
I always perceived it as a mixture of German and Hebrew.
However it's not a creole language in a conceptual sense b/c it was conceived as the language in its own right, in process employing elements of Hebrew and German, as opposed composed from two.
english.stackexchange.com/users/1446/Anderson Silva
Was English itself a creole language in the century or so after the Norman Conquest?
In the first century after the Norman Conquest, people would have spoken either Anglo-Saxon (Old English) or Old Norman.
The latter was used as the language of state.
From what little I understand, these languages were kept separate and Old English, as the language of a subjugated underclass, was in danger of dying out.
From these two languages came Anglo Norman and eventually Middle English.
So far as I know it wouldn't be accurate to say that English was a creole language in the sense of being a subset language used for communications between speakers of Old English and Old Norman.
english.stackexchange.com/users/2614/RedGrittyBrick
A "creole" language is formed by the merging of two parent languages, usually through an earlier rudimentary mixture of the two. Does this make Yiddish a creole language? Was English itself a creole language in the century or so after the Norman Conquest?   My question is really about what constitutes a creole language: what are its hallmarks and most distinguishing features, and do creole languages ever evolve to become "proper" languages (whatever that may mean) in their own right?
Is Yiddish a creole language? And if not, what is it?
english.stackexchange.com
<language-formation>
english.stackexchange.com/questions/6147
english.stackexchange.com/users/2303/Robusto
Yiddish is generally not considered to be a creole language and was conceived as a language in its own right, although there is little agreement as to what it is. Some terms used to describe Yiddish include Pidgin, Creoloid, Fusion Language and Composite Language. As for English, it would not be accurate to describe English as a creole language. Yiddish is a quasi a Germanic language, and includes a large number of Hebrew words. It is known as a Creoloid language. Yiddish is a fusion language with elements of German, Hebrew and Armaic. It was learn through song and theatre. It is not a creole language as such, as it was conceived in its own right, much like English is not a creole language, as it was a subset of a language used to communicate between speakers of Old English.Creole does not mean a combination of languages. It is simply a "pidgin" language that native speakers use. It uses a simple vocabularly.An example of Creole is Haitain Creole. It was not originally intended to be used as a lingua franca.
Yiddish is generally not considered to be a creole language and was conceived as a language in its own right, although there is little agreement as to what it is. Some terms used to describe Yiddish include Pidgin, Creoloid, Fusion Language and Composite Language. As for English, it would not be accurate to describe English as a creole language.  Grammatically, Yiddish is almost entirely Germanic - very close to an older form of High German, with significant borrowings from other languages, such as Polish and Russian.   As such, it is not what most scholars describe as a creole, but it is typically referred to as a Creoloid, much like Afrikaans, Michif, and even African American Vernacular English. Yiddish is called a FUSION language by linguists, (as is English) derived from old High German, beginning around the year 1000in the Rhine Valley.  
Although not a creole language, Yiddish is a language in its own right, which is written in Hebrew characters, is a composite  language stemming from Judeo-German - the languages used by  the Jews who settled in the Rhine  Valley in the Middle Ages. Yiddish is generally not considered to be a creole language, although there is little agreement as to what it is. Some terms used to describe Yiddish include Pidgin, Creoloid, Fusion Language and Composite Language. As for English, it would not be accurate to describe English as a creole language.
 Grammatically, Yiddish is almost entirely Germanic - very close to an older form of High German, with significant borrowings from other languages, such as Polish and Russian.    As such, it is not what most scholars describe as a creole, but it is typically referred to as a Creoloid, much like Afrikaans, Michif, and even African American Vernacular English. Yiddish is called a FUSION language by linguists, (as is English) derived from old High German, beginning around the year 1000in the Rhine Valley.  
There is no agreement as to how to classify the Yiddish language, with people using the term Creoloid, Pidgin, Fusion Language or a Composite Language. English would probably not be accurately described as a creole language. Yiddish is probably not a creole language.