When a word can use both of those suffixes, does it have the same meaning?

For example, 'polysemic' and 'polysemous'. Both from the noun 'polysemy'.

2 Answers 2


In chemistry, such terms almost always have distinct meanings. For example, ferric refers to compounds of Fe³⁺ and ferrous to compounds of Fe²⁺, nitric oxide is NO and nitrous oxide is N₂O, and so on. (Note: I just thought of anhydrous/anhydric, which is an exception.) In other sciences, an -ic and an -ous form sometimes are synonyms (like achromous/achromic), and sometimes aren’t (like autonomic/autonomous).

Non-technical -ic/-ous or -ic/-ious pairs are often, but not always, synonyms (like euphoric/euphorious). There are also some words whose final syllable coincidentally happens to be -ous or -ic and also happen to have a corresponding -ic or -ous word, such as arsenic/arsenious or arsenous, and generic/generous. (Thanks to other users for sharing better examples!)

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    And, by the way, yes, polysemic and polysemous are synonymous. Sep 6 at 22:53
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    What does ETA mean? It certainly isn't "Estimated Time to Arrival" here.
    – iBug
    Sep 7 at 12:49
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    I don’t really understand the last sentence. Arsenous and autologic do not exist, as far as I know. What corresponding forms are you referring to? @iBug It means ‘Edited To Add’. Sep 7 at 13:42
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    @iBug some people seem to use it to mean "Edited to Add". Sep 7 at 13:42
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    @JanusBahsJacquet It’s more commonly spelled arsenious, but the spelling arsenous acid also exists.
    – Davislor
    Sep 7 at 16:24

No, they need not have the same meaning. For example, "generous" and "generic" share a root but have very different meanings (from M-W) despite bearing those suffixes:

generous: "liberal in giving : OPENHANDED" (among other meanings)

generic: "relating to or characteristic of a whole group or class : GENERAL" (among other meanings)

Another answer gives good examples from chemistry.

  • And here I was trying to think of a better example than autologous.
    – Davislor
    Sep 7 at 3:02
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    Also: autonomic vs autonomous. Sep 7 at 12:18
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    But except in chemistry, there is not a systematic difference in meaning.
    – Colin Fine
    Sep 7 at 16:50
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    @LearningEnglish Although Davislor's answer is a good and interesting one, I think this answer serves better as the correct one.
    – paddotk
    Sep 8 at 11:34
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    @ColinFine Maybe, but is there a systematous meaning? Sep 8 at 12:45

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