a length or portion of time.
he had long periods of depression
a punctuation mark (.) used at the end of a sentence or an abbreviation.
As he talked he jabbed the lit end of his cigar into the air as though he were punctuating his sentences by burning periods in the air.
the interval of time between successive occurrences of the same state in an oscillatory or cyclic phenomenon, such as a mechanical vibration, an alternating current, a variable star, or an electromagnetic wave.
To produce a larger effect, the motion must accumulate, and for wave-impulses to accumulate, they must arrive in periods identical with the periods of vibration of the atoms on which they impinge.
a flow of blood and other material from the lining of the uterus, lasting for several days and occurring in sexually mature women who are not pregnant at intervals of about one lunar month until the onset of menopause.
It is common to have heavy blood flow at the beginning of a period and lighter blood flow at the end.
a set of elements occupying an entire horizontal row in the periodic table.
The horizontal rows or periods also have predictable trends in characteristics because as you move left to right in a row only one electron is added changing the atomic number by one.