| Term | Definition |
|---|---|
| Sphere | A round three dimensional object who's surface is the same distance from the center at all points. |
| Axis | An imaginary line around which earth spins. |
| Rotation | The spinning if earth on its axis, which causes day and night to occur. |
| Revolution | Earths yearly orbit around the sun. |
| Ellipse | Elongates, closed curve that describes earths year long orbit around the sun. |
| Solstice | An astronomical event that occurs twice each year as the Sun reaches its highest or lowest excursion relative to the celestial equator on the celestial sphere. |
| Equinox | The time or date (twice each year) at which the sun crosses the celestial equator, when day and night are of equal length (about September 22 and March 20). |
| Moon Phase | The different forms the moon takes in its appearance from earth. |
| New Moon | The phase of the moon when it is in conjunction with the sun and invisible from earth, or shortly thereafter when it appears as a slender crescent. |
| Waxing | When the illuminated part of the moon is growing. |
| Full Moon | The phase of the moon in which its whole disk is illuminated. |
| Waning | When the illuminated section of the moon is decreasing in size. |
