To Condescend

(intransitive) To come down from one's superior position; to deign (to do something).
(intransitive) To treat (someone) as though inferior; to be patronizing (toward someone); to talk down (to someone).
(transitive, rare, possibly nonstandard) To treat (someone) as though inferior; to be patronizing toward (someone); to talk down to (someone).
(intransitive, obsolete) To consent, agree.
(intransitive, obsolete) To come down.

"Condescend" is a catenative verb that takes the to infinitive. See Appendix:English catenative verbs
In sense “to talk down”, the derived participial adjective condescending (and corresponding adverb condescendingly) are more common than the verb itself.
In older usage, "condescend" could be used non-pejoratively (in a sense similar to that of treating someone as inferior) to describe the action of those who socialized in a friendly way with their social inferiors. Now that the concept of social inferiors has largely fallen out of currency, so has this non-pejorative sense. Thus, in w:Pride_and_Prejudice, a character could say of another, "I need not say you will be delighted with her. She is all affability and condescension.”