Developed world in the context of "Urbanization"

In the history of the 20th century, the interwar period, also known as the interbellum (from Latin inter bellum 'between the war[s]'), lasted from 11 November 1918 to 1 September 1939 (20 years, 9 months, 21 days) – from the end of World War I (WWI) to the beginning of World War II (WWII). It was relatively short, yet featured many social, political, military, and economic changes throughout the world. Petroleum-based energy production and associated mechanisation led to the prosperous Roaring Twenties, a time of social and economic mobility for the middle class. Automobiles, electric lighting, radio, and more became common among populations in the first world. The era's indulgences were followed by the Great Depression, an unprecedented worldwide economic downturn that severely damaged many of the world's largest economies.

Politically, the era coincided with the rise of communism, starting in Russia with the October Revolution and Russian Civil War, at the end of WWI, and ended with the rise of fascism, particularly in Germany and Italy. China was in the midst of a half-century of instability and the Chinese Civil War between the Kuomintang, the Chinese Communist Party, and many warlords. The empires of Britain, France, and others faced challenges as imperialism was increasingly viewed negatively and independence movements emerged in many colonies; in Europe, after protracted low-level fighting most of Ireland became independent.

Menstruation (also known as a period, among other colloquial terms) is the regular discharge of blood and mucosal tissue from the inner lining of the uterus through the vagina. The menstrual cycle is characterized by the rise and fall of hormones. Menstruation is triggered by falling progesterone levels, and is a sign that pregnancy has not occurred. Feminine hygiene products are used in order to maintain hygiene during menses.

The first period, a point in time known as menarche, usually begins during puberty, between the ages of 11 and 13. However, menstruation starting as young as eight years would still be considered normal. The average age of the first period is generally later in the developing world, and earlier in the developed world. The typical length of time between the first day of one period and the first day of the next is 21 to 45 days in young women; in adults, the range is between 21 and 35 days with the average often cited as 28 days. In the largest study of menstrual app data, the mean menstrual cycle length was determined to be 29.3 days. Bleeding typically lasts two to seven days. Periods stop during pregnancy and typically do not resume during the initial months of breastfeeding. Lochia occurs after childbirth. Menstruation, and with it the possibility of pregnancy, ceases after menopause, which usually occurs between 45 and 55 years of age.

Abstinence-only sex education (also known as sexual risk avoidance education) is a form of sex education that teaches not having sex outside of marriage. It often excludes other types of sexual and reproductive health education, such as birth control and safe sex. In contrast, comprehensive sex education covers the use of birth control and sexual abstinence.

Evidence does not support the effectiveness of abstinence-only sex education. It has been found to be ineffective in decreasing HIV risk in the developed world. It does not decrease rates of sexual activity or unplanned pregnancy when compared to comprehensive sex education.

Genital herpes is a herpes infection of the genitals caused by the herpes simplex virus (HSV). Most people either have no or mild symptoms and thus do not know they are infected. When symptoms do occur, they typically include small blisters that break open to form painful ulcers. Flu-like symptoms, such as fever, aching, or swollen lymph nodes, may also occur. Onset is typically around 4 days after exposure with symptoms lasting up to 4 weeks. Once infected further outbreaks may occur but are generally milder.

The disease is typically spread by direct genital contact with the skin surface or secretions of someone who is infected. This may occur during sex, including anal, oral, and manual sex. Sores are not required for transmission to occur. The risk of spread between a couple is about 7.5% over a year. HSV is classified into two types, HSV-1 and HSV-2. While historically HSV-2 was more common, genital HSV-1 has become more common in the developed world. Diagnosis may occur by testing lesions using either PCR or viral culture or blood tests for specific antibodies.

The second millennium of the Anno Domini or Common Era was a millennium spanning the years 1001 to 2000. It began on January 1, 1001 (MI) and ended on December 31, 2000 (MM), (11th to 20th centuries; in astronomy: JD 2086667.5 – 2451909.5).

It encompassed the High and Late Middle Ages of the Old World, the Islamic Golden Age and the period of Renaissance, followed by the early modern period, characterized by the European wars of religion, the Age of Enlightenment, the Age of Discovery and the colonial period. Its final two centuries coincide with modern history, characterized by industrialization, the rise of nation states, the rapid development of science, widespread education, and universal health care and vaccinations in the developed world. The 20th century saw increasing globalization, most notably the two World Wars and the subsequent formation of the United Nations. 20th-century technology includes powered flight, television and semiconductor technology, including integrated circuits. The term "Great Divergence" was coined to refer the unprecedented cultural and political ascent of the Western world in the second half of the millennium, emerging by the 18th century as the most powerful and wealthy world civilization, having eclipsed Qing China, Edo Japan, the Islamic world and India. This allowed the colonization by European countries of much of the world during this millennium, including the Americas, Africa, Oceania, and South and Southeast Asia.