Numbers, numbers, everywhere. Many authors I know complain about math and how unforgiving numbers are. But numbers play a very important role in fiction as well. So what are the numerals of power in fiction? Let’s count them off!

One – The loneliest number. This is the number of narrators in most stories, chosen for simplicity. It’s also the number of major changes any given character should have in a single story, so as to keep them recognizable to the audience. It’s not particularly significant to story structure or characterization but rather a guard against doing too much in a given story. Pretty much any time you have to ask yourself “how much should this happen?” The answer is “One time.” Two characters with similar traits? There can be only one. One is the number that maximizes clarity and impact so don’t be afraid to use it when needed.

Two – There’s an intimacy to this number that’s important to preserve. Two is about as many threads of conversation a person can follow. Whenever you have a string of dialog that’s meant to be particularly strong, whether impactful, dramatic, or funny it’s important that you have no more than two speakers in the scene. Lots of speakers may be important at times, due to the nature of what’s being discussed or the situation of the characters, but the height of that conversation should always boil down to just two speakers and the rest should either be tied up in side conversations or just waiting for the climax of the dialog to play out.

Three – This one goes a lot of different places. First off, three characters serve as the foundation of any group in your narrative. That’s because three is the smallest group that allows for both intimacy and exclusion. That is to say, two them can turn against the third. And there’s always the possibility that the two can split up, leaving one betrayed as the other two form a new alliance. Or, if a pair needs someone to step in and arbitrate some disagreement the third is there to fill in. These kinds of character “trinities” are common in fiction. Star Trek, the original series, had Kirk, Spock and McCoy. Star Wars, the classic trilogy, had Han, Luke and Leia. DC Comics has Superman, Batman and Wonder Woman. Each of these triads features three distinct personalities and specialties that make the characters distinct and memorable and allows them to complement each other.

Three is also a good number for plot elements. For example, a set of three important items that must be collected or protected from those seeking to steal them. Three quests to carry out. Three different places to explore. Even if the items, activities or places themselves are different, as in the case of the Japanese sacred treasures (a sword, mirror and jewel) they will all serve the same purpose. In the case of the Japanese treasures, showing that the emperor was divine. A perfect example of this is in Avatar: The Last Airbender, in which the main character is seeking to understand three fundamentally different forces of nature in order to unite them and balance them. Mastering each is a unique task in a unique place but leads to a single end.

Three also serves as a good number for tasks because it lets you have a variety of outcomes for those tasks to build suspense without stretching things out enough that wondering about outcomes becomes boring. Whether things go lose, lose, win or win, win, lose, or some combination of those it can switch things up and be interesting but happens fast enough that the audience isn’t waiting for it to end.

Why three is a number humans place such significance on is hard to pin down. It’s a fairly constant theme in human culture but it’s not clear what abandoning three for some other number would do to storytelling. My personal theory is that three is just an easy number to grasp and by sticking to it you can keep your audience from feeling overburdened by the complexities of your story.

Five – This is another number important to interpersonal dynamics. The ideal group size in fiction seems to be five. Yes, the three are the foundation but five is the perfect number. There are five Power Rangers – to start with – in most seasons of that show for a reason.

A group of five easily breaks down into the two smaller groups of characters. Two can go off on their own for an intimate moment while the other three form the backbone of a situation evolving on the outside of the group. While single stories might not ever build a solid five, instead keeping pairs of other people orbiting around a central three, any franchise that strives for narrative cohesion will build a central five or, at the very least, keep five characters at the center of any given story. TV shows like Firefly, Cheers and Friends all serve as excellent examples of this. No more than five of the central cast are in play in the majority of episodes and often a pair of side characters take center stage with a trio from the main cast.

Five is also the number of a good family set-up, with a mother, father, and children that are younger, older and in the middle. Frequently characters will not have this relation by blood but still relate this way in terms of character dynamics. This means everyone in the audience can recognize their place in the dynamic.

Seven – Seven is considered a “lucky” number in the West (the Easter equivalent is the number eight). It represents completion or divine appointment, so when you group things in batches of seven keep those concepts in mind. It’s a good way to show purity or morality behind concepts as well, as seen in the seven deadly sins and seven noble virtues (the Eight Trigrams in Taoist thought are a sort-of equivalent but probably not something to worry about unless China or Korea is your story’s setting). Seven often works in concert with the number thirteen, which is seven (the number of divine completion) plus six (the number of human frailty). Thirteen is just as unlucky as seven is lucky, possibly more so.

In some traditions ten, twelve and forty are considered numbers of completion as well. They don’t have quite the same cultural cachet as seven and definitely should be used sparingly. They should always be groups of similar things, like forty days or a dozen men, rather than rather disparate things like virtues.

And that’s pretty much all the numbers a writer needs. Single digits is best. But that doesn’t mean that deciding on the numbers isn’t a thing you really need to think about when writing. So don’t eschew math – just modify it to suit being an author.