ineffective vs unable

ineffective and unable both are adjectives.

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

As adjectives, ineffective and unable are synonyms defined as:

Other synonyms of ineffective include ineffectual.

ineffective (adjective)	unable (adjective)
not producing an intended effect	(usually followed by `to') not having the necessary means or skill or know-how
lacking in power or forcefulness	lacking in power or forcefulness
lacking the ability or skill to perform effectively; inadequate	(usually followed by `to') lacking necessary physical or mental ability