Freebase(0.00 / 0 votes)Rate this definition: Portable Network Graphics. Portable Network Graphics is a raster graphics file format that supports lossless data compression. PNG was created as an improved, non-patented replacement for Graphics Interchange Format, and is the most used lossless image compression format on the World Wide Web.
Definition of menopause. 1 : the natural cessation of menstruation that usually occurs between the ages of 45 and 55; also : the period during which such cessation occurs âcalled also climacteric â compare perimenopause. 2 : cessation of menstruation from other than natural causes.
Menstruation is the shedding of the lining of the uterus (endometrium) accompanied by bleeding. It occurs in approximately monthly cycles throughout a woman's reproductive life, except during pregnancy. Menstruation starts during puberty (at menarche) and stops permanently at menopause (see Menopause). By definition, the menstrual cycle begins with the first day of bleeding, which is counted as day 1. The cycle ends just before the next menstrual period. Menstrual cycles normally range from about 25 to 36 days.