Antonyms of adj unable

3 senses of unable

Sense 1
unable (vs. able) -- ((usually followed by `to') not having the necessary means or skill or know-how; "unable to get to town without a car"; "unable to obtain funds")

able (vs. unable) -- ((usually followed by `to') having the necessary means or skill or know-how or authority to do something; "able to swim"; "she was able to program her computer"; "we were at last able to buy a car"; "able to get a grant for the project")

Sense 2
unable (predicate) -- ((usually followed by `to') lacking necessary physical or mental ability; "dyslexics are unable to learn to read adequately"; "the sun was unable to melt enough snow")

INDIRECT (VIA incapable) -> capable -- ((usually followed by `of') having capacity or ability; "capable of winning"; "capable of hard work"; "capable of walking on two feet")

Sense 3
ineffective, ineffectual, unable -- (lacking in power or forcefulness; "an ineffectual ruler"; "like an unable phoenix in hot ashes")

INDIRECT (VIA impotent) -> potent, strong, stiff -- (having a strong physiological or chemical effect; "a potent toxin"; "potent liquor"; "a potent cup of tea", "a stiff drink")

Similarity of adj unable

3 senses of unable

Sense 1
unable (vs. able) -- ((usually followed by `to') not having the necessary means or skill or know-how; "unable to get to town without a car"; "unable to obtain funds")

Sense 2
unable (predicate) -- ((usually followed by `to') lacking necessary physical or mental ability; "dyslexics are unable to learn to read adequately"; "the sun was unable to melt enough snow")
       => incapable (vs. capable) -- ((followed by `of') lacking capacity or ability; "incapable of carrying a tune"; "he is incapable of understanding the matter"; "incapable of doing the work")

Sense 3
ineffective, ineffectual, unable -- (lacking in power or forcefulness; "an ineffectual ruler"; "like an unable phoenix in hot ashes")
       => impotent (vs. potent) -- (lacking power or ability; "Technology without morality is barbarous; morality without technology is impotent"- Freeman J.Dyson; "felt impotent rage")