n. 1
Absence of equality. A statement that of two quantities one is specifically less than (or greater than) another. Symbol: < or ≤ or > or ≥ or ne , as appropriate.
The inequality x is less than y, together with that ylt;z, allows us to deduce the inequality xlt;z.
n. 2
Absence of equality. A condition or state (of social, cultural, or legal matters) that is not equal; especially, such a condition that is thereby also unfair.
The inequality in living standards led to a civil war as the have-nots rebelled.
n. 3
Absence of equality. Unevenness, irregularity.

Forms

Plural: inequalities → inequations, disparities, differences, unevennesses…

Choose the right word

Inequality or Disparity?

Disparity is stronger than inequality, implying that one thing falls far below another; as, the disparity of our achievements when compared with our ideals.

J. C. Fernald, English Synonyms and Antonyms (1914)

Example sentences

disparity 3-D glasses make use of retinal disparity.
injustice I should not close my eyes when I face injustice.

Popularity over time

Word	1850 → 2019	Trend
inequality		rising
unequalness		steady
inequation		rising
disparity		steady
unevenness		falling

Use in printed books, per decade from 1850 to 2019.

By length

4 letters: odds¹
8 letters: imparity
9 letters: diversity⁴, injustice³, prejudice³, disparity⁴
10 letters: difference³, unfairness³, inadequacy⁵, unevenness, inequation, unequality, unlikeness
11 letters: unequalness, inequalness
12 letters: irregularity⁶
13 letters: inconsistency⁵, disproportion, dissimilarity⁶

The small number after each word is its number of syllables (diversity⁴ = 4 syllables).

In other languages

Français: inégalité
Italiano: disparità
Español: desigualdad
Català: desigualtat