inequality

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

• noun The condition of being unequal.
• noun An instance of being unequal.
• noun Lack of equality, as of opportunity, treatment, or status.
• noun Social or economic disparity.
• noun Lack of smoothness or regularity; unevenness.
• noun Variability; changeability.
• noun Mathematics An algebraic relation showing that a quantity is greater than or less than another quantity.
• noun Astronomy A deviation from uniformity in the apparent motion of a celestial body.

from The Century Dictionary.

• noun Lack of equality in character or attributes; unlikeness between things of the same kind; diversity; disparity: as, inequality in size, numbers, etc.; the inequality of the fingers.
• noun Lack of equality in the state or condition of a person or thing; want of uniformity of relation, level, surface, etc.; variation or variable ness; unevenness: as, inequalities of temper; inequalities of rank or fortune; inequalities of the earth's surface.
• noun Injustice; partiality.
• noun In astronomy, the deviation in the motion of a planet or satellite from its uniform mean mo tion.
• noun In algebra, an expression of two unequal quantities connected by either of the signs of inequality ⟩ or ⟨; thus, a ⟩ b, signifying that a is greater than b, and a ⟨ b, signifying that a is less than b, are inequalities.

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

• noun The quality of being unequal; difference, or lack of equality, in any respect; lack of uniformity; disproportion; unevenness; disparity; diversity
• noun Unevenness; lack of levelness; the alternate rising and falling of a surface
• noun Variableness; changeableness; inconstancy; lack of smoothness or equability; deviation; unsteadiness, as of the weather, feelings, etc.
• noun Disproportion to any office or purpose; inadequacy; competency.
• noun (Alg.) An expression consisting of two unequal quantities, with the sign of inequality (> or <) between them.
• noun (Astron.) An irregularity, or a deviation, in the motion of a planet or satellite from its uniform mean motion; the amount of such deviation.

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

• noun An unfair, not equal, state.
• noun mathematics A statement that of two quantities one is specifically less than (or greater than) another. Symbol: < or ≤ or > or ≥, as appropriate.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun lack of equality