Writers have many tools at their disposal to convey different ideas in their writing, and not all of these tools come in the form of words. Punctuation can often convey as much meaning as words, and they can indicate ideas words sometimes can't--such as silence, pauses, and emotional cues such as excitement. One such form of punctuation is the ellipsis, which is meant to indicate either omitted text, a pause within a sentence, or an idea trailing off into silence.
An ellipsis is typically indicated by a series of three periods (...) and can occur anywhere in a sentence, depending on the intended meaning. An ellipsis does not always come in the form of three dots. It may also be indicated by an M-dash (--) or three asterisks (***), but the most common form is the three periods (...). This technique has led to the ellipsis's colloquial name, the "dot dot dot."
Because an ellipsis does not necessarily mean the same thing in all instances of its appearance, the reader must be responsible for deciphering the meaning of its presence. When placed in a sentence, an ellipsis may indicate to the reader that a word or words has been omitted, but it may also mean that a silence or pause has been indicated. The real meaning is largely up to the reader to decide. Here is an example:
John flew to...Mexico.
The ellipsis in this sentence may indicate that the specific location in Mexico has been omitted,
John flew to Oaxaca, Mexico.
Or, it may indicate that the speaker of the sentence has paused before mentioning Mexico, perhaps to think about where John went, or perhaps for some other intention, such as hiding John's specific location within Mexico. In this case, the reader is not given enough contextual information to make the determination, but in most cases, the reader will have gleaned enough information from previous sentences and paragraphs to decipher what the writer has intended by using an ellipsis.
The ellipsis is not limited to writing in English, either. When making long lists of numbers, mathematicians and students may use the ellipsis to indicate a continuation of the list to a certain point. For example, when counting by tens to 100, one might write the following:
10, 20, 30, ...100.
This indicates the person counting should continue counting by ten past thirty all the way to one hundred, but the ellipsis saves space on the page by cutting out what should be obvious to the astute reader.