Relating to something that changes suddenly and unpredictably without warning. (1)

1. One of a group of highly luminous yellow or orange super giant stars, whose brightness varies in a regular manner as the result of stellar pulsations.
2. A yellow super giant star that varies regularly in brightness every few days or weeks as a result of pulsations.

The time that a Cepheid variable takes to pulsate is directly related to its average brightness; the longer the period, the brighter the star.

Cepheus is a constellation of the northern hemisphere near Cassiopeia (a W-shaped constellation in the northern hemisphere near Polaris) and Draco (a large faint constellation of the northern hemisphere).

1. An economic magnitude describing behavior that takes place over time and is therefore meaningful to a unit of time: Examples of flow variables in economics include: the value of exports (dollars per year), demand for foreign exchange (euros per day), and migration (people per month).

2. Activities that occur over time: Income is a flow variable that occurs per week, per month, or per year.

A variable star typified by the red giant Mira Ceti.

The light curve is irregular, with a varying range of brightness and of a period between peaks of brightness.

1. A star whose brightness changes over time.
2. A star whose luminous output varies significantly with time.

Such variation may be regular; that is, eclipsing variable stars, or irregular, as with flare stars.

In addition, the variation can be intrinsic, because of changes within the star itself, or extrinsic, as the result of the interaction of one star with another.

A load that requires low torque at low speeds and increasing torque as the speed is increased, with very high torque being required at high speeds.