the beginning of something: its first point or earliest stage; in adverb form, "first," "at first," or "formerly."
At its core this is a noun for the opening point of something, built from the verb meaning "to begin." It names where a thing starts: the start of the barley harvest, the first year of a king's reign, the outset of a prophet's ministry, the opening words of a speech.
The same word slides easily into an adverb. Paired with a small prefix ("at the beginning"), it fans out into two everyday shades. One is priority: "first," ahead of everyone else, as when Israel asks which tribe should march up first into battle. The other is earlier time: "formerly" or "before," as when Jacob's sons recall the first trip they made down to Egypt. In both, the picture is the same starting point, seen either as the head of a line or as a time now past.
A famous line stretches the word past pure time. "The fear of the LORD is the beginning of wisdom" (Proverbs 9:10) uses it for the entry point and foundation of wisdom, not merely the first item on a list to be checked off and left behind. Its close relative רֵאשִׁית, another common word for "beginning," works the same ground and can lean further toward "the chief or best part."