Autumn, interchangeably known as fall in North America, is one of the four temperate seasons. Fall marks the transition from summer into winter when the arrival of night becomes noticeably earlier and the temperature cools considerably. One of its main features is the shedding of leaves from deciduous trees.
However, according to the Irish Calendar, which is based on ancient Gaelic traditions, autumn lasts throughout the months of August, September and October, or possibly a few days later, depending on tradition. In Australia and New Zealand, autumn officially begins on 1 March and ends on 31 May.
The word autumn comes from the ancient Etruscan root autu- and has within it connotations of the passing of the year. It was borrowed by the neighbouring Romans, and became the Latin word autumnus. After the Roman era the word continued to be used as the Old French word autompne (automne in modern French), and was later normalised to the original Latin. In the Medieval period there are rare examples of its use as early as the 12th century, but by the 16th century it was in common use.
Before the 16th century, harvest was the term usually used to refer to the season, as it is common in other West Germanic languages to this day (cf. Dutch herfst, German Herbst and Scots hairst). However, as more people gradually moved from working the land to living in towns, the word harvest lost its reference to the time of year and came to refer only to the actual activity of reaping, and autumn, as well as fall, began to replace it as a reference to the season.
Association with the transition from warm to cold weather, and its related status as the season of the primary harvest, has dominated its themes and popular images. In Western cultures, personifications of autumn are usually pretty, well-fed females adorned with fruits, vegetables and grains that ripen at this time. Many cultures feature autumnal harvest festivals, often the most important on their calendars.
Still extant echoes of these celebrations are found in the autumn Thanksgiving holiday of the United States and Canada, and the Jewish Sukkot holiday with its roots as a full-moon harvest festival of “tabernacles” (living in outdoor huts around the time of harvest). There are also the many North American Indian festivals tied to harvest of autumnally ripe foods gathered in the wild, the Chinese Mid-Autumn or Moon festival, and many others.
Autumn is associated with the Halloween season (influenced by Samhain, a Celtic autumn festival), and with it a widespread marketing campaign that promotes it, in the United States. The television, film, book, costume, home decoration, and confectionery industries use this time of year to promote products closely associated with such a holiday, with promotions going from early September to 31 October, since their themes rapidly lose strength once the holiday ends, and advertising starts concentrating on Christmas.
Television stations and networks, particularly in North America, traditionally begin their regular seasons in autumn, with new series and new episodes of existing series debuting mostly during late September or early October (series that debut outside the fall season are usually known as midseason replacements). A sweeps period takes place in November to measure Nielsen Ratings.