There are two languages: Yiddish, and Yiddish-in-English. Although they appear to be the same language, these two languages actually have completely different vocabularies and are spoken by completely different segments of the population. To lessen the miscommunication between the Yiddish speakers and the Yiddish-in-English speakers, I have prepared definitions of the most easily confused words.
Yiddish: a bastard. That mamzer salesman tried to rip me off!
Yiddish-in-English: a smart, shrewd individual. My genius nephew! Such a smart little mamzer!
Yiddish: insolence, impudence, the least desirable of character traits. Then he has the chutzpah to tell me that I need to pay for shipping!
Yiddish-in-English: guts. My nephew has the chutzpah it takes to be a good salesman.
Oy Vey (interjection)
Yiddish: Oh no. His check bounced? Oy vey!
Yiddish-in-English: I'm Jewish! You also read Phillip Roth? Oy vey!
Yiddish: non-Jew. My neighbors are all Goyim.
Yiddish-in-English: a pejorative word for non-Jew. Speakers of Yiddish-in-English never use the word "Goy" themselves. They only refer to other people using the word "Goy." The Hasids act aloof around the "Goyim."
Yiddish: African-American. My Mexican cleaning lady was deported. But I found a new one, a shvartze.
Yiddish-in-English: Like "Goy" this word is only used when quoting a Yiddish speaker. And then my old senile mother started to scream, "Get that shvartze out of here!"
Yiddish: crazy. That guy is meshuga.
Yiddish-in-English: crazy, but not just crazy. It's like... ummmm. You can't explain it in English. It just what we call in Yiddish "meshuga." That guy is meshuga.
That's all folks!