The Hebrew noun tor means a row, order, turn, or succession. It appears in descriptions of ordered rows of stones in priestly breastplates (Exodus 28:17-20), decorative rows (Song of Songs 1:10), and turns or appointments (Esther 2:12, 15). A related word tor also means turtledove, but this is a different root.
The theme of divine order runs throughout Scripture, and tor captures the principle of things in their proper row or place. The High Priest's breastplate had four rows (turim) of precious stones — twelve stones for twelve tribes, all in ordered tor, carried over the priest's heart before God. Order in worship reflects the orderly character of the Creator. The Book of Esther's use of tor for the maidens' turns before the king (Esther 2:12, 15) has been read typologically — each in her appointed time, fulfilling her appointed role. Esther's turn became the pivot of Jewish salvation. Appointed order serves divine purpose.