Here's a joke I didn't understand fully until I heard it in English here in the U.S.:
Two old Jewish friends, Chaim and Mordechai, decided they'd had enough with anti-Semitism in Hungary and emigrated to the U.S. After they got themselves established they both met up one day to explore their new country. Happening upon a supermarket, they ventured inside and were amazed how big it was, and how much food there was everywhere. They split up and just went their own ways, wondering wide-eyed down the aisles. After about an hour Chaim ran into Mordechai in a back aisle, crying hysterically.
"Mordi, tell me what is the matter? Why are you crying?"
"O Chaim, we've wasted our time. We could have stayed in Hungary!"
"Why?" Mordechai asked.
"Chaim, they're as bad here as back home! I was looking at all the wonderful kinds of fruit they have when I asked the clerk in my halting English why there were so many different kinds of oranges. Do you know what he told me? He told me that these oranges were for eating, and those oranges over there were for Jews!" [Joke: "Jews" = "juice"]
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Clearly as has been discussed "anti-Semitism" has its limit as a term, but in practice it has come to mean a prejudicial belief that Jews in particular have some sort of negative innate qualities, as individuals or as a group. It's a belief that their very Jewishness is a negative matter, a crime.
I laugh though at the attempts here to
define Jews and Jewishness, because it raises a critical point. What is a Jew? Is it someone who adheres to the Jewish faith? What then about Jews who become secular? Is there a Jewish ethnicity? If so, does that mean that Ethiopian Jews are less Jewish than Sephardic or Ashkenazi Jews? Was the Nazi revival of Phrenology a valid way to determine who is a Jew? When confronted by a subordinate about some Jewish friends he was saving, Himmler is supposed to have exploded, "
I say who is a Jew!" Modern humans like to believe that ethnic identity is in our blood, that it is an ancient and all-pervasive aspect of our identities and lives, but in reality ethnicity is a very fluid thing subject to constant change.
Anti-Semitism is a prejudice, a kind of racism and as such no different from any other ethnic or group prejudice. The difference for Anti-Semitism of course is its extent. Anti-Semitism is a phenomenon that has had a powerful impact on European history (and by extension, Europe's colonies' histories), and continues to today. It's true that there are some Jewish groups who overuse the anti-Semitic charge, (Remember Jerry Seinfeld's uncle Leo on his show, who for every person who crossed his path he would say, "Jerry - did you see that? He's an Anti-Semite!" and Jerry would just role his eyes...

I miss that show!) and there are some who confuse legitimate criticism of Israeli policies with anti-Semitism, but such people are a minority. American Blacks have a similar problem with those among them who see slants where there are none. But the recent spate of attacks in Europe, especially France, show that some anti-Semitism is indeed alive and in no way can be equated with legitimate protests against Israeli policies.