Do the adjectives “reliable” and “dependable” have the same exact meaning?
If not, what is the difference and when is best to use each of them?
The OED gives the following definitions of reliable and dependable:
Both definitions list the other word in their definitions, with no special qualifiers attached. In addition, both words use the word trustworthy, also without qualifiers. Therefore, it is safe to say that the two are synonyms and may be equally used.
Here is the discussion of reliable and dependable in Webster's Dictionary of Synonyms (1942):
Here is the corresponding discussion in James Fernald, Funk & Wagnalls Handbook of of Synonyms, Antonyms & Prepositions, revised edition (1947):
Interestingly, the first edition of Fernald's dictionary (1896) opens with the comment that "The word reliable has been sharply challenged, but seems to have established its place in the language." Fernald then goes on to show why the criticism "on the ground that the suffix -able can not properly be added to an intransitive verb" is baseless, and then compares reliable to trustworthy and trusty—but not to dependable, which it doesn't cover at all.
Finally, here is the discussion of the two terms in S.I. Hayakawa, Choose the Right Word (1968):
As with all books that attempt to delineate fine distinctions between words that have similar meanings, the ones I cite here inhabit a gray zone where distinguishing between actual differences in preponderant informed usage (on the one hand) and the authors' desire to establish differences that may not be widely observed in practice (on the other) can be difficult.
Obviously "reliable" means "can be relied upon" and "dependable" means "can be depended upon", but both my Webster's and etymological dictionary give near-identical usages, even using the other as synonyms.
Google Ngram viewer shows "reliable" as far more common than "dependable".
Reliable and dependable are interchangeable when they refer to things (i.e. a clock), or to oneself vis-a-vis someone else. However, there is a nuance when the terms apply to someone else vis-a-vis oneself. In this case reliable implies a decision to commit oneself to another and to acept the consequences in the event of failure. With dependable, the commitment is not a free choice. (Source: The Heritage Illustrated Dictionary of the English Language, International Edition, McGraw Hill.)
protected by tchrist Feb 26 at 1:21
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