According to the Merriam-Webster online dictionary, the meanings of responsible, answerable, and payable are

responsible: liable to be called on to answer

answerable: liable to be called to account

payable: that may, can, or must be paid.

They all include the meaning of obligation rather than the straightforward meaning of the suffix, the one of capability as in durable, whose meaning in the online dictionary is

durable: able to exist for a long time without significant deterioration in quality or value.

In the case of responsible, it seems possible to argue that the suffix gives to the word the meaning of freedom or opportunity that the adjective able has as in

You are able to skate on the lake today. The ice is thick enough.

Then, the sentence below may mean he has the right to decide everything about recruiting and training.

He is responsible for recruiting and training new staff.

But, such interpretation seems impossible for the other two words.

Why does the suffix able sometimes have the meaning of obligation in words such as payable or answerable?

(I found two similar questions. One is about how to tell whether the suffix has the meaning of ability or that of obligation. My question is about why the suffix has the meaning of obligation. The other has not been given a proper answer because, in my opinion, the words used as examples are uncommon words.)

  • 2
    The suffix -able/-ible is a modal, and all modals have epistemic and deontic senses. Deontic senses have to do with permission and obligation. Responsible (for) refers to an obligation -- what must be done. Payable asserts that something must be paid, and answerable has the same sense as responsible. Commented Mar 2, 2023 at 2:31
  • 2
    Isn't this a duplicate of How did "-able" semantically shift to mean "requiring"? But the answers are not great.
    – Laurel
    Commented Mar 2, 2023 at 3:24
  • Thank you @JohnLawler . I didn't know suffixes have a function as a modal. Could you give me other examples of suffixes (or perhaps prefixes) which are also modals? Or, -able is exceptional in this regard?
    – Aki
    Commented Mar 2, 2023 at 3:36
  • @Laurel Yes, it is basically the same question as mine, but I think the answers there are not convincing.
    – Aki
    Commented Mar 2, 2023 at 4:26
  • 1
    Please take more care in your use of English. Two basic mistakes in your title are hardly a good advertisement for your question. If you have a word processor on your computer, set the language to English and then do a grammar check. It won’t be perfect, but it might pick up the difference in forms of the verb to have, between “it has” and “it does have”.
    – David
    Commented Mar 2, 2023 at 14:01

2 Answers 2


The suffix -able/-ible, like the word able, is a modal; be able to is one paraphrase of one sense of can.

Like all modals, -able has two senses:

  • a deontic permission/obligation sense
    This veil is permissible; That word is not publishable.


  • an epistemic possibility/probability sense (most common in negatives)
    This equation is impossible/improbable; The house is barely habitable.

If you look, you'll find all modals have dual meanings; some have more.


Why does suffix -able sometimes has the meaning of obligation in words such as payable or answerable?

I'm not sure why you'd think there must be a reason for the suffix -able to have "the meaning of obligation" and, more importantly, that we should be able to find such a reason.

If that's a legitimate question, you can also ask, "Why does the suffix -able sometimes have the meaning of capability?", which I'd think you know you can't.

M-W does say the suffix has two meanings:

variants or less commonly -ible
1 : capable of, fit for, or worthy of (being so acted upon or toward) —chiefly in adjectives derived from verbs
2 : tending, given, or liable to

(Boldface mine.)

  • I don't ask "Why does the suffix -able sometimes have the meaning of capability?" because the adjective able has the meaning.
    – Aki
    Commented Mar 2, 2023 at 5:14
  • @Aki Just because an adjective has a certain meaning doesn't mean a suffix with the same or similar form as the adjective should have the same meaning.
    – JK2
    Commented Mar 2, 2023 at 5:26
  • 1
    So, why is that? I think it is a legitimate question. Do they have different etymological origins, for example? Or, the adjective able too has the meaning of obligation, which I think John Lawler's answer suggests.
    – Aki
    Commented Mar 2, 2023 at 5:52
  • 1
    Both the adjective able (mostly as a predicate adjective with infinitive complement He's able to do that now) and the suffix -able from the same source are modals semantically, and have several meanings (and many idioms). Modality is a very complex topic. Commented Mar 2, 2023 at 14:57
  • 1
    @JK2 But, meanings don't come from nowhere. I think I have the answer thanks to John Lawler. A modal word, whether it is an adjective or a suffix, has both epistemic and deontic senses. Which sense comes up to the surface depends on the context. I even think that there could be a context the adjective able has the meaning of obligation, even though the closest example I have come up with is "You could ask before you borrow my car" from Practical English Usage by M. Swan"
    – Aki
    Commented Mar 3, 2023 at 7:33

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.