A Hebrew noun meaning beginning, first, chief part, firstfruits, choicest. From rosh (head), it denotes the first in time, rank, or quality. It is the very first word of the Bible (in construct form): bereshith — 'In the beginning.' It also refers to the firstfruits offering — the first and best portion given to God.
As the opening word of Scripture, reshith frames the entire biblical narrative: everything begins with God. In Proverbs 1:7, the 'beginning (reshith) of knowledge is the fear of the LORD' — wisdom itself has a starting point, and it's God. The firstfruits offering (Deuteronomy 26:2) taught Israel that the first and best belongs to God — an act of faith that trusts God for the rest. Paul identifies Christ as the 'firstfruits of those who have fallen asleep' (1 Corinthians 15:20), using the same concept: Christ's resurrection is the reshith — the beginning, the guarantee, the first portion of the harvest of resurrection.