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Who knows eighteen?

Please cite/link your sources, if possible. After about one business day, I will:

  • Upvote all interesting answers.

  • Accept the best answer.

  • Go on to the next number.

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10 Answers 10

up vote 3 down vote accepted

Eighteen are the years before one gets hitched. (Ben Shemonah Esrei LiChupah: Avos 5:21)

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Does? Should? May? – Isaac Moses Apr 16 '10 at 17:09
I heard the Biblical hint for this is that "Adam" appears 18 times before the first use of "Ish" – Shalom Apr 16 '10 at 18:39
Another one is that the verse about who the Kohen Gadol may marry (Lev. 21:13) starts with the word והוא, whose numerical value is 18 (Baal Haturim on this verse). – Alex Apr 16 '10 at 19:54
Isaac. it is too complicated to get into and besides, none of those words fit the meter of the tune! – Yahu Apr 19 '10 at 3:53
Checkmark due to value added by interesting comments. – Isaac Moses Apr 19 '10 at 17:46

Eighteen is the value (in maneh) of the linen clothing that the Kohen Gadol wore for his first entry into the Holy of Holies each Yom Kippur, according to the majority opinion (Yoma 34b).

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Shemona Asar was the number of berachot in the Shemona Esrei, before the addition of "shover oyvim umakhni'a zeidim" (Berachot 28b)

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It is called Birchas Haminim. – Yahu Apr 16 '10 at 17:00

Eighteen are the minimum (or according to Rambam, the absolute) number of days in a woman's cycle, according to the original Torah law: seven of niddah (Lev. 15:19), and eleven of zivah (based either on Lev. 15:25, or an unwritten halachah le-Moshe mi-Sinai - Talmud, Niddah 72b-73a).

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$18 is how much an aliyah costs

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... In some shuls. – Daniel Jul 10 '15 at 17:43

18 is the gematriya of chai

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Also of "Yach". – Double AA Mar 25 '12 at 6:09
Also of חטא.​​​​​​​​​​​​​​​ – Double AA Feb 15 '13 at 4:28

There are eighteen sins for which the punishment is misa bide shamayim but for which one can get lashes. Source: Rambam, Sanhedrin 19.

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Lag B'Omer is on 18 Iyur

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Only in our fixed calendar (or in the variable calendar if Nisan happened to have 30 days). – Double AA Feb 14 '13 at 23:09

Eighteen is the age of the [modern] Draft. (Thanks Isaac!)

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Many modern ones, yes, but not the Bibilical one: mi.yodeya.com/questions/1104/esrim-mi-yodeya/1105#1105 – Isaac Moses Apr 20 '10 at 17:04
This is really a comment, not an answer to the question. Please use "add comment" to leave feedback for the author. – Isaac Moses Aug 21 '12 at 21:00

Eighteen is the age at which one should finish learning the entire Talmud according to one opinion (15 to start learning (Pirkei Avos), and it is a machlokes (in kiddushin I think) if it takes 3 or 5 years to complete it).

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Sourcing that machloket in kiddushin would be valuable. (Even better would be to show that the opinions in kiddushin had ever seen the pseudo-mishna in avot about ages.) – Double AA Feb 2 '14 at 5:57

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