Suppose we want to include a quote in a passage we are writing. Suspect that the quote is too long. Now presume the quote is "The dog quickly ran to the water dish after he had been quickly chasing a fast cat through the humid forest." Perhaps we want to omit "through the forest." We would then write:
"The dog quickly ran to the water dish after he had been quickly chasing a fast cat..."
The new sentence still makes sense, but the use of the ellipsis mark shows the reader that something is missing.
We sometimes also use an ellipsis mark to indicate a pause when someone is speaking, or an unfinished sentence.
However, we don't use an ellipsis mark with a space.
