expediency

1. Appropriateness to the purpose at hand; fitness.
2. Adherence to self-serving means: an ambitious politician, guided by expediency rather than principle.
3. A means; an expedient.
4. Obsolete. Speed; haste.

noun

Something used temporarily or reluctantly when other means are not available: expedient, makeshift, shift, stopgap. See help/harm/harmless, substitute.

Definition: appropriateness
Antonyms: impracticality

The noun has one meaning:

Meaning #1: the quality of being suited to the end in view
  Synonym: expedience
  Antonym: inexpediency (meaning #1)

Quotes:

"Custom adapts itself to expediency." - Publius Cornelius Tacitus

"No man is justified in doing evil on the ground of expediency." - Theodore Roosevelt

"The end justifies the means." - Proverb

"Nobody is forgotten when it is convenient to remember him." - Benjamin Disraeli