Last night Y-H-B was sitting in the audience of a classical music concert (four Brandenburg Concertos by Bach) when he overheard a man behind him (who looked to be in his sixties or seventies) say to a companion the phrase “patently incorrect.” What was significant about this utterance was the fact that he pronounced the first word in the British manner, i. e., [péɪtntli], with the stressed vowel of pate, not pat, as would be the case for the American pronunciation of patent. The British pronunciation has long been recommended by American dictionaries as the correct form for the meaning of patent, as defined in the OED Online as ‘Of a fact, quality, phenomenon, etc.: clear, evident, obvious’; cf. the Merriam-Webster Unabridged definition ‘readily visible or intelligible: evident, obvious’.
Now, it is true that contemporary American dictionaries qualify the pronunciation exhibited by my fellow concert-goer (an American, judging by his speech) as “Chiefly British,” whereas fifty years ago this form of the vowel would be the sole one codified for this meaning (as in “patently incorrect”). This whole matter brings up the interplay of grammar, norm, and habit in any living language. What is grammatically possible is always constrained at any stage of the language’s history by usage, dictated in the modern period (from the Enlightenment on in Europe and America) by academies and various other norm-setters. Norms are set not only by institutions but by speakers who adhere to them and thereby propagate a certain usage, especially where (what used to be called “free”) variation is possible. The prestige accruing to speakers by virtue of their status in society necessarily also enhances the prestige of their speech, such that learners and other speakers will adopt variants heard in the speech of such prestigious persons. This process over time results in speech habits, which are just like the whole ensemble of behavioral traits that define us as human beings in constituting (letzten Endes) part of the stylistic repertory that reaffirms the conception of style as a fundamentally cognitive category.