The Tetragrammaton is the four-letter Hebrew theonym יהוה (YHWH), the name of God in the Hebrew Bible. The four letters, written and read from right to left (in Hebrew), are yodh, he, waw, and he. The name may be derived from a verb that means "to be", "to exist", "to cause to become", or "to come to pass".
The books of the Torah and the rest of the Hebrew Bible contain this Hebrew name. Observant Jews do not pronounce יהוה; instead they replace it with a different term, whether in addressing or referring to the God of Israel - like Adonai ("My Lord") or Elohim ("gods", or HaShem ("The Name") in everyday speech.