first quarter
Noun: 1. A primary lunar phase: The specific point or period when the Moon has completed approximately one-quarter of its orbit around the Earth, as seen from Earth. At this phase, exactly half of the Moon's disk is illuminated, and the illuminated portion is on the right side (in the Northern Hemisphere). 2. The shape of the Moon during this phase: The visible appearance of the Moon during this time, resembling a "half-moon" that is waxing (increasing in illumination).
The term "first quarter" is used almost exclusively in the context of astronomy to describe a specific lunar phase. It is a proper noun phrase and is typically used with the definite article "the." * The Moon will reach its first quarter on Friday. * During the first quarter, you can see a perfect half-moon in the evening sky. * The first quarter is one of the four primary phases of the Moon.
- In Navigation and Calendars: Historically, the lunar phases, including the first quarter, were used for timekeeping and navigation.
- The farmers planted according to the cycle of the Moon, often after the first quarter.
- Lunar Phase / Moon Phase (noun): Any of the recurring appearances of the Moon as seen from Earth, including new moon, first quarter, full moon, and last quarter.
- Waxing Gibbous (noun): The lunar phase that follows the first quarter, where more than half but not all of the disk is illuminated and growing.
- Last Quarter (noun): The complementary lunar phase where the Moon has completed three-quarters of its orbit, showing the left half illuminated (in the Northern Hemisphere).
- First Quarter in other contexts (e.g., finance, sports, academic year) refers to the first of four equal periods. CRITICAL NOTE: This is a separate, compound usage of the words "first" and "quarter." The primary and distinct meaning of the term "first quarter" as a single lexical unit is the lunar phase.
- The company's profits increased in the first quarter of the fiscal year. (This is a different, context-dependent meaning.)
- Half Moon (Waxing) (noun): A descriptive, non-technical term for the Moon's appearance during the first quarter phase. Note: "First quarter" is the precise astronomical term.
There are no common idioms or phrasal verbs specifically for the astronomical term "first quarter."
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the first fourth of the Moon's period of revolution around the Earth
