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iom
יומ
In general, 'iom' means “day”.
More broadly, 'iom' may refer to a periodic temporal phenomenon. The exact length of time varies with a great degree of flexibility. Although in some cases “today” seems to be the correct implication, in many cases it is used to refer to a person's entire lifespan. In some case it seems to indicate “time” in general. For example, consider the phrase “in the days of Noah”; this is intended as a time corresponding to Noah's life, rather than a specific set of exact days. 'iom' may or may not be cognate with “eon”.
Because of this flexibility, there is some ambiguity inherent in the term that is not always appreciated in traditional translations. For example the classic interpretation of the opening chapter of Genesis relies heavily on a strict interpretation of a day as a 24 hour period which might not be warranted. This interpretation is assumed because of the appearance of several cycles of day and night, light and dark, which certainly does make logical sense, but may not be the only possible interpretation.
On the other hand there are contextual examples which clearly contrast several different units of time, thus fairly explicitly presenting 'iom' as a day. An excellent example of this is found in 1 Chronicles 21:12, in which Ihoh presents a dilemma to David; to choose between 3 curses: 3 years of famine and starvation, 3 months of slaughter in war, or 3 days of direct cursing and destruction by Ihoh himself.
see also iomim