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definitions

preferable

[pref-er-uh-buh l, pref-ruh- or, often, pri-fur-]
adjective
  1. more desirable.
  2. worthy to be preferred.

Origin of preferable

From the French word préfsptérable, dating back to 1640–50. See prefer, -able
Related formspref·er·a·bil·i·ty, pref·er·a·ble·ness, nounpref·er·a·bly, adverbnon·pref·er·a·bil·i·ty, nounnon·pref·er·a·ble, adjectivenon·pref·er·a·ble·ness, nounnon·pref·er·a·bly, adverbun·pref·er·a·ble, adjectiveun·pref·er·a·ble·ness, nounun·pref·er·a·bly, adverb
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
British Dictionary definitions for preferability

preferable

adjective
  1. preferred or more desirable
Derived Formspreferability or preferableness, noun

usage

Since preferable already means more desirable, one should not say something is more preferable or most preferable
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Word Origin and History for preferability

preferable

adj.

1640s, from or on model of French préférable, from préfér (see prefer). OED notes preferrable is better English but has not prevailed. Related: Preferably.

Online Etymology Dictionary, © 2010 Douglas Harper