whereas

from The American Heritage® Dictionary of the English Language, 5th Edition.

• conjunction It being the fact that; inasmuch as.
• conjunction While at the same time.
• conjunction While on the contrary.
• noun An introductory statement to a formal document; a preamble.
• noun A conditional statement.

from The Century Dictionary.

• The thing being so that; considering that things are so: implying an admission of facts, sometimes followed by a different statement, and sometimes by inference or something consequent, as in the preamble to a law or a resolution.
• While on the contrary; the fact or case really being that; when in fact.
• Where.

from the GNU version of the Collaborative International Dictionary of English.

• adverb obsolete At which place; where.
• conjunction 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.
• conjunction 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.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adverb obsolete Where (that).
• conjunction In contrast; whilst on the contrary.
• conjunction It being the fact that
• conjunction Inasmuch as
• noun A clause, as in legal documents, stating whereas.