Who knows eighty-one?

Please cite/link your sources, if possible. At some point in the next few days, I will:

  • Upvote all interesting answers.

  • Accept the best answer.

  • Go on to the next number.


A woman who gives birth to a female brings an olah and a chatas on the 81st day after the birth.

  • As we've asked before, can you prove more 81-ness, or is it just an 80 spin-off? (Not that I have super-better-answers.) – Shalom Aug 23 '10 at 18:16
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    The fun thing about this Day 81: Meseches Kinim. ("Combinatorics for rabbis.") – Shalom Aug 23 '10 at 18:21
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    What about day 41? – Dave Aug 23 '10 at 19:36
  • Woops, in hachi nami. – Shalom Aug 24 '10 at 1:05
  • "Combinatorics." Now that's a good word! – Dave Aug 24 '10 at 3:27

Every book and sub-book of Tanach contains a word with Gematria 81; the most-common word is אנכי. I'd heard some parshanut/drush a while back about how אנכי is the "more complex me" as opposed to אני, "simpler me." Is anyone familiar with this?


Niddah 30b records a gruesome experiment performed by Cleopatra to determine how long it takes an embryo to develop: She took pregnant maidservants who had been sentenced to death, and examined the contents of their wombs. According to the Gemara's second version (in the name of R' Yishmael), she determined that a female embryo is not developed until day 81 (as opposed to a male embryo, which is already developed by day 41). The Sages, however, rejected this conclusion as having been established by fools (אין מביאין ראיה מן השוטים), since the experiment was not adequately controlled.


There is at least one word that appears exactly once in chumash.
At least one word appears exactly twice in chumash.
At least one word appears exactly three times in chumash.
There is a word that appears exactly eighty times in chumash.
There is no word that appears exactly eighty-one times in chumash. 81 is the smallest number with this property.

  • Did you count or do you have a source? – Gershon Gold Oct 20 '10 at 19:41
  • Computer program. – Shalom Oct 20 '10 at 19:49
  • How are you counting words? Do variations in n'kudos make for different words? If so, do variations in cantillation? If variations in n'kudos do but variations in cantillation do not, what about variations in stress (emphasis)? Are you counting the k'ri or the k'siv? If the k'siv, and variations in n'kudos count, what are you considering the n'kudos of a word that has a k'ri different from its k'siv? Are you counting a series of words connected by hyphens as one word or as several words? – msh210 Oct 20 '10 at 20:34
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    Using this (unvowelized, uncantillated, unstressed) text, as it would appear in a scroll: mechon-mamre.org/i/t/x/x0.htm Words are demarcated by spaces or hyphens. I make no promises that this is the way; just the way I did it. – Shalom Oct 20 '10 at 21:24

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