Natural series and dramatic series:

The natural series of events is the mundane things that happen as we go about our lives. We need to mention them occasionally in fiction to fill in the pauses between dramatic events and give a sense of reality.

The dramatic series of events makes up a story. Real life seldom provides these (or we wouldn’t need fiction). A natural series will not naturally become a dramatic series.

Coincidences commonly happen in the natural series, but should be kept out of the dramatic series, because despite happening all the time in real life, they’re implausible in fiction.

#shortfiction Damon Knight