The Hebrew noun yom means day, time, or a defined period. It is one of the most common nouns in the Old Testament, occurring over 2,300 times. It can refer to a literal daytime period (as opposed to night), a full 24-hour day, or a longer, indefinite period of time depending on context.
Yom is central to the creation narrative (Genesis 1), where God creates in six "days" and rests on the seventh. It also forms the basis of the Sabbath commandment. The prophetic phrase "the Day of the LORD" (yom YHWH) is a major eschatological concept referring to God's decisive intervention in history — a time of both judgment and salvation. The word's flexibility allows Scripture to speak of God's activity in both ordinary time and cosmic, redemptive time.