(astronomy) the particular appearance of a body's state of illumination (especially one of the recurring shapes of the part of Earth's moon that is illuminated by the sun) | a wheeled vehicle that has two wheels and is moved by foot pedals |
(physical chemistry) a distinct state of matter in a system; matter that is identical in chemical composition and physical state and separated from other material by the phase boundary | a single complete execution of a periodically repeated phenomenon |
any distinct time period in a sequence of events | a periodically repeated sequence of events |
a particular point in the time of a cycle; measured from some arbitrary zero and expressed as an angle | a series of poems or songs on the same theme |
| an interval during which a recurring sequence of events occurs |
| the unit of frequency; one hertz has a periodic interval of one second (named for Heinrich Rudolph Hertz) |