a punctuation mark (.) placed at the end of a declarative sentence to indicate a full stop or after abbreviations | the warning signal that begins a period of preparation for an enemy air attack |
the monthly discharge of blood from the uterus of nonpregnant women from puberty to menopause | the condition in which combat aircraft are airborne and ready for an operation |
an amount of time | the time period during which military and civilian agencies are prepared for an enemy air attack |
the interval taken to complete one cycle of a regularly repeating phenomenon | |
a unit of geological time during which a system of rocks formed | |
the end or completion of something | |
(ice hockey) one of three divisions into which play is divided in hockey games | |