Consistency is being free of contradiction. Logical consistency, consistency of approach, a lack of consistency.
In logic, a consistent set of statements is one that cannot all be false together by contradiction — and inconsistency is fatal, since anything at all follows from a contradiction. In ordinary use it means behaving the same way over time, which is what makes people and systems predictable. In cooking, consistency means the thickness of a mixture, which is a third sense entirely.
1nounconsistencyBeing free of contradiction.
“The lawyer pointed out a lack of consistency between the witness's two statements.”
2nounthicknessThe thickness of a mixture.
“Beat it to roughly the consistency of cream.”
Too few real examples of this word to estimate which sense is commonest.
consistency is a quality of coherence.
Consistent plus -ency, from Latin consistere, to stand firm — con plus sistere, to stand. Consist, insist and resist come from the same standing.
Latin
consistens
English
consistent
English, today
consistency
Built from
by surface analysis, consistent + -cy, consistence + -y or consist + -ency. consistent Borrowed from Latin consistens. Latin consistens, present participle of cōnsistō (“to agree with; to continue”), from con- (ultimately from Proto-Indo-European ḱóm (“beside, by, near, with”)) + sistō (“to cause to stand; to place, set”) (ultimately from Proto-Indo-European stísteh₂ti (“to be standing up; to be getting up”), from the root steh₂- (“to stand (up)”)). by surface analysis, consist + -ent.
Etymology from Wiktionary, CC BY-SA