I really need your help regarding this matter, In spite of all the hard work in finding a clear difference that makes me use -able over -ed, I couldn't find a definite rule.

For example, valued vs valuable, reputed vs reputable, desirable vs desired

is there such a simple way to differentiate and know which one to use?

  • To use a made-up example: glurk -able: you can glurk it. glurk -ed : someone has already done the action of glurking it. For example, replaceable: can be replaced. replaced: someone has already done replacing on it. That's a simplification, but it might help.
    – stangdon
    Apr 20, 2018 at 14:13

1 Answer 1


You cannot find any reference to such a rule because there is no such rule.

In general, the past participle of any transitive verb can be turned into an adjective. Similarly, adjectives can be formed by adding the suffix able to the root of a regular transitive verb. (An irregular verb like eat may have an irregular analog like edible.) The two adjectives thus formed usually carry the same or very similar meanings, but if the able form becomes a common word, it is likely to take on a distinct meaning.

A valued book means only that someone does or did value the book for some personal reason. A valuable book means more than that someone values the book personally: it asserts that the book has intellectual importance or substantial market value.

In the case of reputed and reputable, their meanings have become almost opposite. If I say Joe is a reputed lawyer, I am saying that others apparently believe Joe to be a lawyer but that I personally am doubtful whether he is a competent lawyer or even a lawyer at all. Reputed conveys doubt: it does not convey personal conviction. On the other hand, reputable implies that the speaker has no reason to doubt the common opinion. If I say Joe is a reputable lawyer, I am saying that as far as I know Joe is a competent and honest lawyer and deserves a good reputation as a lawyer.

Just because two words derive from the same root does not make them synonyms.

DELAYED EDIT: A comment by the OP pointed out that my original answer may be misinterpreted. When I said that able can be added as a suffix to regular transitive verbs, I did not mean to imply that such a suffix can never be added to an intransitive verb. I am not aware of any regular transitive verb where able cannot be added as a suffix. If there are any such verbs, they must be rare. On the other hand, I am aware of common intransitive verbs that cannot grammatically be changed that way. Comeable, beable, becomeable are not idiomatic expressions.

  • I agree with this and especially the assertion "because there is no such rule." That is a categorical statement, is it not? You have zeroed in on how these morphemes work and how one must take care in not assuming their meanings are the same. [upvote for clarity and explanation]. A curious point: we say "ill-reputed" but the opposite "well-reputed" though possible is not widespread.
    – Lambie
    Apr 20, 2018 at 14:17
  • what about the verb 'agree'? it is intransitive but there are two adjectives of it (agreed and agreeable) what is the difference between them? also, can you point out the difference between accepted and acceptable? Apr 20, 2018 at 16:31
  • @ Ghassan I shall edit my answer. I did not mean to imply that only transitive verbs can have able added as a suffix. What I meant is that transitive verbs generally can be transformed in that way, but many intransitive cannot be. Thanks for pointing out that my original answer may be misconstrued. Apr 20, 2018 at 21:25
  • @ Lambie Thank you for the kind words and the up vote. I know: I can't help myself with the categorical statements, but I have joined a 12-step program and am making progress on that issue. Apr 20, 2018 at 21:46

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