Wikipedia's definition of soap operasdefinition of soap operas is:
A soap opera is an ongoing drama serial on television or radio, featuring the lives of many characters and their familial, platonic and intimate relationships.1 The term soap opera originated from radio dramas being sponsored by soap manufacturers.2
https://en.wikipedia.org/wiki/Soap_opera
So I might change the definition to something like this:
A soap opera is an ongoing drama serial on television or radio, primarily featuring the day to day lives of many characters, who are more or less ordinary people, and their familial, platonic and intimate relationships, in more or less ordinary situations, and created to be primarily an example of the soap opera genre.1 The term soap opera originated from radio dramas being sponsored by soap manufacturers.2
In recent decades more and more dramatic programs in the USA have become more serialized and less episodic. Thus they come to resemble soap operas in some ways. ButBut those shows are often primarily intended to be examples of the crime, fantasy, historical, horror, medical, police, suspense, spy, science fiction, western, etc. genres, and not primarily soap operas.
Each season of 2424 (2001-2010) was extremely serialized, telling of events in a 24 hour period in a series of hour long episodes. But 24 (2001-2010) was about political intrigue, action, counter terrorism, espionage, etc., and 24 (2001-2010) is described as "an American action drama television series" in Wikipedia,not as a soap opera.
https://en.wikipedia.org/wiki/24_(TV_series)
One important method of telling a soap opera is its broadcast schedule. In the USA a prime time soap opera, like Dallas, would broadcast first run episodes once a week for about twenty odd weeks each year, and have reruns the other weeks of the year, with a schedule very similar to those of prime time shows that are not soap operas. But daytime soap operas tend to broadcast first run episodes five days a week, 52 weeks a year, with no reruns.
Another soap opera example is PassionsPassions (1999-2008) which was a soap opera with strong supernatural elements. One of the main characters was a witch, Tabitha, who was so powerful that she brought a doll, Timmy, to life, & he become another character on the show.
https://en.wikipedia.org/wiki/Passions
(curiously, according to one sitethis site, Passions (1999-2008) is in the same fictional universe - imaginatively labeled as Group 10 - as a few other series, including all the Star trekTrek series.)
http://www.poobala.com/crossoverlist.html
Another famous example is Get Smart (1965-1970), a situation comedy which was also a spy series. The protagonists were in deadly danger in almost every episode, and killed a lot of people, which is very unusual for a situation comedy.
So it is possible for a series to be both a soap opera and a horse opera, a soap opera and a space opera, a soap opera and a spy drama, a soap opera and a medical show, etc., etc., and some people may be able to suggest a number of examples of such hybrid, multi genre-genre series.