A name for God, used above all in the Hebrew Bible — what Christians call the Old Testament. In Hebrew the name is written with four letters, roughly YHWH, and ancient Hebrew did not write vowels, so nobody today knows for certain how it was said. "Yahweh" is scholars' best guess at the old pronunciation, and it is the form you find in books about history and religion. This matters in practice: many Jewish people do not say the name aloud at all, out of respect, and read "Adonai" (the Lord) instead when the four letters appear. Most English Bibles follow the same custom and print "the LORD" in small capital letters wherever the Hebrew has YHWH. So "Yahweh" is a word you will meet far more in a textbook, a lecture or an academic article than in a church service. You may also meet "Jehovah", an older English attempt at the same four letters that most scholars now think was a mistake — the vowels of Adonai accidentally read onto the consonants of YHWH. Jehovah's Witnesses, whose group name comes from that form, still use it. Yahweh, Jehovah and "the LORD" all point to the same name.