a wheeled vehicle that has two wheels and is moved by foot pedals | a bicycle with two sets of pedals and two seats |
a single complete execution of a periodically repeated phenomenon | an arrangement of two or more objects or persons one behind another |
a periodically repeated sequence of events | |
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) | |