The Torah uses 3 terms that all appear to mean "leavened food" (from English definitions that I could find):

  • חמץ and שאור are mentioned in Exodus 12:15:

שִׁבְעַ֤ת יָמִים֙ מַצּ֣וֹת תֹּאכֵ֔לוּ אַ֚ךְ בַּיּ֣וֹם הָרִאשׁ֔וֹן תַּשְׁבִּ֥יתוּ שְּׂאֹ֖ר מִבָּתֵּיכֶ֑ם כִּ֣י ׀ כָּל־אֹכֵ֣ל חָמֵ֗ץ וְנִכְרְתָ֞ההַנֶּ֤פֶשׁ הַהִוא֙ מִיִּשְׂרָאֵ֔ל מִיּ֥וֹם הָרִאשֹׁ֖ן עַד־י֥וֹם הַשְּׁבִעִֽי׃

  • מחמצת is mentioned in Exodus 12:19:

שִׁבְעַ֣ת יָמִ֔ים שְׂאֹ֕ר לֹ֥א יִמָּצֵ֖א בְּבָתֵּיכֶ֑ם כִּ֣י ׀ כָּל־אֹכֵ֣ל מַחְמֶ֗צֶת וְנִכְרְתָ֞ה הַנֶּ֤פֶשׁ הַהִוא֙ מֵעֲדַ֣ת יִשְׂרָאֵ֔ל בַּגֵּ֖ר וּבְאֶזְרַ֥ח הָאָֽרֶץ׃

Are there differences in the meaning of these terms, and do these definitions have halachic implications either in terms of the prohibition of not eating, seeing, suing it and / or the punishment for violation?

  • חמץ and מחמצת are from the same root.
    – Scimonster
    Mar 10, 2015 at 18:27
  • 2
    "ואיסור החמץ ואיסור השאור שבו מחמצין, אחד הוא." ~ Rambam Hilchot chametz u'matza 1:2
    – Rish
    Mar 10, 2015 at 18:30
  • @Scimonster - I realize that. But the 1st seems to be a noun and the 2nd a verb. And I assume there may be some halachic definition between the two.
    – DanF
    Mar 10, 2015 at 18:30

1 Answer 1


Afaik, seor is leaven, or sourdough starter or pre ferment, meaning basically flour and water which is allowed to, well, ferment. This product is used to start the leavening process of a different batch of dough. Chametz is the dough made from the starter culture. Machmetzes is an umbrella term for all items falling into the category of something that is leavened which includes both the seor and chametz mentioned earlier.

See http://en.m.wikipedia.org/wiki/Sourdough for some basic info on the bread making process that was used for thousands of years until recently when yeast starters were identified, separated, and marketed.

  • So, it seems that "se'or" is the agent that causes fermentation? If that's the case, there are many things that cause fermentation including hydrogen peroxide with baking soda. Yet, this combo is allowed on Pesach.
    – DanF
    Mar 10, 2015 at 19:01
  • @DanF that may be true. I don't think seor is translated as a blanketed starter, it means the starter from the dough process. If you have access to Rabbi Meiselman's book, he had a very interesting chapter about chametz and the five species that exhibit the specific process that the Torah disallows on Pesach.
    – user6591
    Mar 10, 2015 at 19:05
  • Providing a source for the claims in its first paragraph would vastly increase the value of this answer.
    – msh210
    Mar 11, 2015 at 19:33
  • @msh210 agreed. But this is how these psukim were explained to me and based on their translations this seems like the way Rabbi Hirsch and Rabbi Kaplan understood them, but there is no smoking gun where they say this is what you thought, but it really means etc. The words are just translated and taken for granted that we would understand.
    – user6591
    Mar 11, 2015 at 19:44

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