unable vs ineffectual

unable and ineffectual both are adjectives.

Word	Noun	Adjective	Verb	Adverb
unable	No	Yes	No	No
ineffectual	No	Yes	No	No

As adjectives, unable and ineffectual are synonyms defined as:

Other synonyms of unable include ineffective.

unable (adjective)	ineffectual (adjective)
(usually followed by `to') not having the necessary means or skill or know-how	not producing an intended effect
lacking in power or forcefulness	lacking in power or forcefulness
(usually followed by `to') lacking necessary physical or mental ability	producing no result or effect