The Hebrew shabuah means a week or period of seven days, from sheva (H7651, seven). It can also refer to a 'week of years' (seven years). The plural shavuot gives the name to the Feast of Weeks (Pentecost), celebrated seven weeks after Passover.
The seven-day week is not a natural astronomical cycle but a divine institution from Creation (Genesis 2:2-3). The shabuah embeds the Sabbath rhythm into time itself — work six, rest one, glorifying God by resting in His completed work. The Feast of Shavuot (Weeks) celebrates the wheat harvest and became associated with the giving of the Law at Sinai. In Acts 2, Pentecost (Greek for fifty days) — another name for Shavuot — becomes the occasion for the outpouring of the Holy Spirit. Daniel's 'seventy sevens' (shivim shabuim, Daniel 9:24-27) is the most complex prophetic use: 70 weeks of years, the countdown to the Messiah's arrival and the events of the end.