period

A length of time.

“There was a period of confusion following the announcement.”

A period of time in history seen as a single coherent entity; an epoch, era.

“Food rationing continued in the post-war period.”

The punctuation mark “.” (indicating the ending of a sentence or marking an abbreviation).

The length of time during which the same characteristics of a periodic phenomenon recur, such as the repetition of a wave or the rotation of a planet.

Female menstruation.

“When she is on her period, she prefers not to go swimming.”

A section of an artist's, writer's (etc.) career distinguished by a given quality, preoccupation etc.

“This is one of the last paintings Picasso created during his Blue Period.”

Each of the divisions into which a school day is split, allocated to a given subject or activity.

“I have math class in second period.”

Each of the intervals into which various sporting events are divided.

“Gretzky scored in the last minute of the second period.”

The length of time for a disease to run its course.

An end or conclusion; the final point of a process etc.

A complete sentence, especially one expressing a single thought or making a balanced, rhythmic whole.

A specific moment during a given process; a point, a stage.

A row in the periodic table of the elements.

A subdivision of an era, typically lasting from tens to hundreds of millions of years, see Appendix: Geologic timescale.

A Drosophila gene, the gene product of which is involved in regulation of the circadian rhythm.

Two phrases (an antecedent and a consequent phrase).

The length of an interval over which a periodic function, periodic sequence or repeating decimal repeats; often the least such length.

End point, conclusion.

To come to a period; to conclude.

To put an end to.

Designating anything from a given historical era.

“a period TV commercial”

Evoking, or appropriate for, a particular historical period, especially through the use of elaborate costumes and scenery.

That's final; that's the end of the matter (analogous to a period ending a sentence); end of story

“I know you don't want to go to the dentist but your teeth need to be checked, period!”