an amount of time
a certain time in the life of a person or the history of a country
a full stop
"a time period of 30 years"
"hastened the period of time of his recovery"
"Picasso's blue period"
"ganoid fishes swarmed during the earlier geological periods"
"death put a period to his endeavors"
"a change soon put a period to my tranquility"
"the women were sickly and subject to excessive menstruation"
"a woman does not take the gout unless her menses be stopped"
"the semen begins to appear in males and to be emitted at the same time of life that the catamenia begin to flow in females"
"in England they call a period a stop"
Lunar gravity should draw the probe into an orbit which has a period of about 10 hr.
A planet with..the same period of rotation..as Earth.
出自： C. Sagan
误 There are six lesson period in a normal school day.
正 There are six lesson periods in a normal school day.
误 During those years of turmoil, we stayed on a farm for a long period of time.
正 During those years of turmoil, we stayed on a farm for a long time.
析 误句中的period of是多余的,应删去。