In a way that is clearly true, certain, and cannot be doubted or argued against.
From Greek 'apodiktikos' (proved, demonstrated), derived from 'apodeiknynai' (to demonstrate clearly). The '-ical' and '-ly' suffixes add the adverbial quality to an adjective meaning absolute certainty.
The root literally means 'to show away from' in Greek—as if you're removing all doubt by pointing so clearly at the truth that it's impossible to miss or deny.
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