αδύναμος

Etymology: From Ancient Greek ἀ- (a-) 'not' + δύναμις (dúnamis) 'power, strength'. The root δύναμις gives us English words like 'dynamic', 'dynamo', and 'dynamite'. The prefix α- is the same as English 'a-' meaning 'not' or 'without', as in 'amoral' or 'atypical'.