A variant form is a different glyph for a character, encoded in Unicode through the mechanism of variation sequences: sequences in Unicode that consist of a base character followed by a variation selector character. A variant form usually has a very similar appearance and meaning as its base form. The mechanism is intended for variant forms where, generally, if the variant form is unavailable, displaying the base character does not change the meaning of the text, and may not even be noticeable by many readers. Unicode defines two types of variation sequences: