Whereas is used to set one fact against a different one. He likes cats, whereas she likes dogs. Whereas the first is cheap, the second is not.
It contrasts without contradicting, which is what separates it from but — both halves are true. In legal drafting a whereas clause sets out the background before the operative terms, and old contracts are full of them.
1prepositionwhereasUsed to set one fact against a different one.
“My brother loves sport, whereas I prefer reading.”
whereas is a connective.
Where plus as. The word first meant simply where, and the contrasting sense grew from that in the fourteenth century.
From where + as; first attested in the meaning of "where" in the 14th century. Compare thereas.
Etymology from Wiktionary, CC BY-SA