A character is a feature that can be measured, counted, described, or otherwise expressed. It is an abstract entity. Petal color is a character. Plant height is a character. Position 33 from the end of a gene is a character.
Characters have states .
In taxonomy, some characters are more equal than other characters, but which characters these are varies from group to group. First of all, one needs to decide if a character is a good taxonomic character for the plants that one is studying. This means a character that is useful in determining to which group a plant belongs. The character varies less within putative groups than between them. If this is not the case, either the character is not useful or the groups are bad.