Which punctuation mark is used where one or more letters are omitted from several origin words called contractions?

The punctuation mark used where one or more letters are omitted from several origin words called contractions is the apostrophe (').

For example:

* don't (contraction of "do not")

* can't (contraction of "cannot")

* I'm (contraction of "I am")

The apostrophe marks the position of the missing letters.