"Mazel tov" or "mazal tov" (Hebrew/Yiddish: "מזל טוב", Hebrew: "mazal tov"; Yiddish: "mazel tov"; lit. "good luck") is a phrase used to express congratulations for a happy and significant occasion or event.
Etymology and pronunciation 
While the words mazal (or mazel in Yiddish; "luck" or "fortune") and tov ("good") are Hebrew in origin, the phrase is of Yiddish origin, and was later incorporated into Modern Hebrew.
While the Yiddish pronunciation of mazel has the stress on the first syllable, the modern Hebrew word "mazal" has the stress on the last syllable, as is standard in modern Hebrew.
Similarly the Yiddish שלימזל, transliterated as shlimazl ("misfortune"), also made its way into US English (as shlemozzle, schlimazel) in the 20th century.
In Polish, the word ślamazara, also derived from Yiddish shlimazl, denotes a person who is slow, sluggish, or lifeless.
Although mazel tov literally translates to "good luck", the phrase is not used in the way that the expression "good luck" is typically used in English (i.e. "I wish you good luck"). It rather means "good luck has occurred" or "your fortune has been good" and is an acknowledgment of this fact (i.e. "lucky you"). The phrase "mazel tov!" parallels the use of the phrase "congratulations!" and conveys roughly that "I am pleased this good thing has happened to you!"
The phrase for wishing good luck to occur in Hebrew, in the way "good luck" does in English, is b'hatzlacha (בהצלחה), literally meaning "with success."
In the diaspora, "mazel tov!" is a common Jewish phrase, such as after a bar or bat mitzvah or a wedding, the congregation may be inclined to shout "Mazel Tov!" For instance, at a Jewish wedding, after the groom breaks the glass everyone yells "Mazel Tov!" In addition it is one of the most well known cultural references that non-Jews know regarding Jews.
See also 
|Look up mazel tov in Wiktionary, the free dictionary.|
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- Moss, Aron. "What Does 'Mazel Tov' Mean?". Chabad.org. Retrieved 2009-06-02.