Inequality, n.; pl. Inequalities.
Etymology: [L. inaequalitas.]
1. The quality of being unequal; difference, or want of equality, in any respect; lack of uniformity; disproportion; unevenness; disparity; diversity; as, an inequality in size, stature, numbers, power, distances, motions, rank, property, etc. There is so great an inequality in the length of our legs and arms as makes it impossible for us to walk on all four. Ray. Notwithstanding which inequality of number, it was resolved in a council of war to fight the Dutch fleet. Ludlow. Sympathy is rarely strong where there is a great inequality of condition. Macaulay.
2. Unevenness; want of levelness; the alternate rising and falling of a surface; as, the inequalities of the surface of the earth, or of a marble slab, etc. The country is cut into so many hills and inequalities as renders it defensible. Addison.
3. Variableness; changeableness; inconstancy; lack of smoothness or equability; deviation; unsteadiness, as of the weather, feelings, etc. Inequality of air is ever an enemy to health. Bacon.
4. Disproportion to any office or purpose; inadequacy; competency; as, the inequality of terrestrial things to the wants of a rational soul. South.
4 more senses
5. (Alg.)
An expression consisting of two unequal quantities, with the sign of inequality (> or <) between them; as, the inequality 2 < 3, or 4 > 1.
6. (Astron.)
An irregularity, or a deviation, in the motion of a planet or satellite from its uniform mean motion; the amount of such deviation.
Shades of meaning
Fernald has no entry of its own for inequality; he lists it under difference.
Where he writes about it:
Disparity is stronger than inequality, implying that one thing falls far below another; as, the disparity of our achievements when compared with our ideals. — from difference