(Internet) The period of time at the launch of a new top-level domain or second-level domain during which trademark owners may register domain names containing their trademarks (to prevent cybersquatting).

plural of periodic structure

(Britain, informal, plural only) Underwear worn by a woman or girl during menstruation, typically old, cheap, or of a dark colour in case of staining.

(grammar) A sentence whose main clause appears at the end, after other, especially dependent, clauses. / (physics) A structure made of bays coupled through one or more coordinates.

(biology) The period, after excitation, during which a membrane recovers its polarization and is not able to respond to a second stimulus.

a work of the screen that evokes a particular historical period

(astronomy) The roughly 1460-year period of time between successive alignments of the first days of the Egyptian civil calendar and the observational Sothic year.

(psychology, biology) A maturational stage in the lifespan of an organism during which the nervous system is especially sensitive to certain environmental stimuli.

(historical) The history of Japan covering the years from AD 710 to 794. Empress Gemmei established the capital of Heijō-kyō (present-day Nara).

Sexual intercourse during menstruation.