(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).

(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.

plural of sunrise period

(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

plural of Sothic 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.

plural of ovulatory period

plural of critical period

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