King James Dictionary 
Whereas, adv. s as z. where and as.
1. When in fact or truth, implying opposition to something that precedes.
Are not those found to be the greatest zealots, who are most notoriously ignorant? Whereas true zeal should always begin with true knowledge.
2. The thing being so that considering that things are so implying an admission of facts, sometimes followed by a different statement, and sometimes by inferences or something consequent, as in the law style, where a preamble introduces a law.
Whereas wars are generally causes of poverty--
3. Whereat at which place. 4. But on the contrary. See No. 1.
Webster's Dictionary 
(1): ( adv.) At which place; where.
(2): ( conj.) Considering that; it being the case that; since; - used to introduce a preamble which is the basis of declarations, affirmations, commands, requests, or like, that follow.
(3): ( conj.) When in fact; while on the contrary; the case being in truth that; although; - implying opposition to something that precedes; or implying recognition of facts, sometimes followed by a different statement, and sometimes by inferences or something consequent.