disjunctive conjunction
Definition - A conjunction, such as but, that
(1) expresses a choice between two mutually exclusive possibilities or
(2) establishes a contrasting or opposing relationship.

Example -
The boy was quick-witted but slow-footed.

Etymology -
It derives from the Latin disjungere, separate.

Oxford English Dictionary -
Its first citation is from 1628:
"That axiome is disiunct, whose band is a disiunctiue Coniunction."
(T. Spencer, Logick, 244)

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