Complex sentence: Seventeenth of Tammuz, the seventeenth day on the Hebrew calendar month of Tammuz, is a half-day (dawn to dusk) fast in Judaism.
Split into simpler sentences: Seventeenth of Tammuz (שבעה עשר בתמוז Hebrew: Shiva Assar BeTammuz) is the seventeenth day on the Hebrew month of Tammuz. It is a half-day (dawn to dusk) fast in Judaism.