BBC Radio's The Archers, first broadcast in 1950, is the world’s longest-running radio soap opera; the world's longest-running television soap opera is Coronation Street, first broadcast on ITV in 1960.
The first serial considered to be a "soap opera" was Painted Dreams, which debuted on October 20, 1930 on Chicago radio station WGN. Early radio series such as Painted Dreams were broadcast in weekday daytime slots, usually five days a week, when most of the listeners would be housewives; thus, the shows were aimed at and consumed by a predominantly female audience. The first nationally broadcast radio soap opera was Clara, Lu, and Em, which aired on the NBC Blue Network at 10:30 p.m. Eastern Time on January 27, 1931.
One of the defining features that makes a television program a soap opera, according to Albert Moran, is "that form of television that works with a continuous open narrative. While Spanish language telenovelas are sometimes called "soap operas," telenovelas have conflicts that get resolved and a definite ending after (more or less) a year of daily weekday airing. But with soap operas each episode ends with a promise that the storyline is to be continued in another episode". In 2012, Los Angeles Times columnist Robert Lloyd wrote of daily dramas, "Although melodramatically eventful, soap operas such as this also have a luxury of space that makes them seem more naturalistic; indeed, the economics of the form demand long scenes, and conversations that a 22-episodes-per-season weekly series might dispense with in half a dozen lines of dialogue may be drawn out, as here, for pages. You spend more time even with the minor characters; the apparent villains grow less apparently villainous."
Soap opera storylines run concurrently, intersect and lead into further developments. An individual episode of a soap opera will generally switch between several different concurrent narrative threads that may at times interconnect and affect one another or may run entirely independent to each other. Each episode may feature some of the show's current storylines, but not always all of them. Especially in daytime serials and those that are broadcast each weekday, there is some rotation of both storyline and actors so any given storyline or actor will appear in some but usually not all of a week's worth of episodes. Soap operas rarely bring all the current storylines to a conclusion at the same time. When one storyline ends, there are several other story threads at differing stages of development. Soap opera episodes typically end on some sort of cliffhanger, and the season finale (if a soap incorporates a break between seasons) ends in the same way, only to be resolved when the show returns for the start of a new yearly broadcast.
Evening soap operas and those that air at a rate of one episode per week are more likely to feature the entire cast in each episode, and to represent all current storylines in each episode. Evening soap operas and serials that run for only part of the year tend to bring things to a dramatic end-of-season cliffhanger.
In 1976, Time magazine described American daytime television as "TV's richest market," noting the loyalty of the soap opera fan base and the expansion of several half-hour series into hour-long broadcasts in order to maximize ad revenues. The article explained that at that time, many prime time series lost money, while daytime serials earned profits several times more than their production costs. The issue's cover notably featured its first daytime soap stars, Bill Hayes and Susan Seaforth Hayes of Days of Our Lives, a married couple whose onscreen and real-life romance was widely covered by both the soap opera magazines and the mainstream press at large.
The main characteristics that define soap operas are "an emphasis on family life, personal relationships, sexual dramas, emotional and moral conflicts; some coverage of topical issues; set in familiar domestic interiors with only occasional excursions into new locations". Fitting in with these characteristics, most soap operas follow the lives of a group of characters who live or work in a particular place, or focus on a large extended family. The storylines follow the day-to-day activities and personal relationships of these characters. "Soap narratives, like those of film melodramas, are marked by what Steve Neale has described as 'chance happenings, coincidences, missed meetings, sudden conversions, last-minute rescues and revelations, deus ex machina endings.'" These elements may be found across the gamut of soap operas, from EastEnders to Dallas. Due to the prominence of English-language television, most soap-operas are completely English (or in the case of a foreign soap opera, dubbed into English). However, several South African soap operas started incorporating a multi-language format, the most prominent being 7de Laan, which incorporates Afrikaans, English, Zulu and several other Bantu languages which make up the 11 Official Languages of South Africa (the subtitles are always in English).