tactful

As a noun taxonomy

is the science or the technique used to make a classification.

As an adjective tactful is

possessing tact; able to deal with people in a sensitive manner.

As adjectives the difference between tactful and condescending

is that tactful is possessing tact; able to deal with people in a sensitive manner while condescending is assuming a tone of superiority, or a patronizing attitude.

As a verb condescending is

present participle of lang=en.