expletive & explicative

expletive (EK spli tiv)
A word used to fill a space in a communication (written or verbal) that does not add meaning to the communication and is often considered crude or obscene: “The editor of the newspaper did not approve of the writers using expletives in their text.”
explicative (EK spli kay” tiv, ik SPLIK uh tiv)
Providing a detailed and logical explanation: “The speaker provided an explicative introduction to his topic.”
The advice columnist in the local newspaper provided an explicative explanation why the use of an expletive in polite conversation is not appropriate.