The title refers to a space in time when two or more related or unrelated events occur simultaneously. When we experience this phenomenon it usually isn’t earth shaking although it does provide an item of conversation that can be shared.
On the other hand, using coincidence in a fictional sense is dangerous because it immediately challenges the reader to hold onto disbelief at the same time that the reader’s inner voice is shouting wait a minute.
If an author uses a coincidental meeting to begin his or her tale the inappropriateness becomes glaringly apparent. It might even result in an otherwise good story being consigned to the oblivion of being unread.
Coincidence is much like the god in the machine device that early writers used to solve the painted-into-a-corner problem with the plot. Both devices strain the reader’s ability to suspend disbelief and have usually been consigned to the same trash can as hackneyed and trite phrases. However, when an author does revert to using the coincidental appearance of a character or event a modern reader throws up his or her metaphorical hands and is bumped out of the story. Only dogged determination will cause the reader to once again take up the tale, perhaps to find that disbelief can once again be suspended to enjoy an otherwise well-told piece of fiction.