A week is called shavu’a (שָׁבוּעַ) in Hebrew,

A week is called shavu’a (שָׁבוּעַ) in Hebrew, from a root word sheva (שֶׁבַע) that means seven. Seven is the number of holiness and completion, and the first verse of Torah has seven words (בְּרֵאשִׁית בָּרָא אֱלהִים אֵת הַשָּׁמַיִם וְאֵת הָאָרֶץ). In six days God created the heavens and the earth, and on the seventh day he rested and set it apart as sacred (Gen. 2:3). The holiday of Shavuot (שָׁבוּעוֹת), or "weeks," marks the "Jubilee of Passover," which occurs after we count 7x7 (49) days from the day following Passover until we reach Sivan 6 (which this year begins Tuesday June 3rd at sundown). Since Shavuot occurs on the 50th day after Passover, the Greek translators of the Torah called it "Pentecost" (πεντηκοστή). Shavuot marks the goal or climax of Passover season, commemorating both the anniversary of the giving of the Torah at Sinai as well as the giving of the Holy Spirit to the followers of Messiah (Acts 1:8; 2:1-4).
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