Yod is the smallest letter of the Hebrew alphabet, drawn as little more than a single stroke with a small decorative flourish, called a kotz, at its tip, and Jewish tradition treats the correct formation of even that tiny flourish as legally significant: a scribe who omits or malforms the kotz shel yod, the tip of the yod, can invalidate an entire Torah scroll despite the letter otherwise appearing intact, a standard of precision without close parallel among the other letters. The phrase kotzo shel yod has passed into ordinary Hebrew idiom for the smallest conceivable detail, in much the way the Greek alphabet's own smallest letter, iota, gave English the idiom not one iota from Matthew 5:18, a verse widely read as echoing this same Jewish emphasis on the letter's minimal but indispensable form, discussed elsewhere in this atlas.
Because every other Hebrew letter is traditionally described as built up from combinations of the yod's basic stroke, some Kabbalistic sources treat Yod as the graphic seed from which the rest of the alphabet unfolds, a symbolic reading distinct from Yod's place among the Sefer Yetzirah's twelve simple letters covered elsewhere in this atlas. Yod is also the first letter of the tetragrammaton, the four-letter name of God central to Jewish reverence for the divine name, a placement that reinforces, in a quite different context, the same sense found in the kotz tradition that even the smallest and least conspicuous Hebrew letter can carry outsized weight.