Learn English – difference between “entrée” and “entry”

I think the difference is in degree. It's similar to the difference between large/huge/gigantic or small/tiny/miniscule. In some contexts, you may be able to substitute any of those words, but due to common usage or word origin or whatever other factors, there is an understood subtle scale.

So, if you have relevant facts to discuss, they may or not be important, but they are related to the matter at hand. But if you have pertinent facts to discuss, they have precise or logical relevance to the discussion. They absolutely should not be overlooked. Pertinent facts are always relevant, but relevant facts are not necessarily pertinent.

One reason why this may be the case is that pertinent could also be used as a synonym for apt (ie. strikingly appropriate) but relevant doesn't really have that meaning. If I said you wrote an "apt answer" to this question how would you feel? What if I said it was a "pertinent answer?" Or "relevant answer?"

I think most people would feel that calling it a relevant answer is nearly a mild insult. Oh yeah, it's related, but not close to perfect.

AAVE/Black English is an identifiable dialect; a hypothetical "White English" could only be identified and unified as being "other than Black English". There are large number of "White Englishes", several of them endemic to the United States, and each of them is identified separately. When considering grammar (which, in the linguistic sense means considerably more than mere word order and tense formation and so on), AAVE has unifying, distinguishing features, whether the speakers are in the originating areas, in the Loyalist diaspora, in Nova Scotia, in Africa (as the remnants of the Colonization) or in the Dominican Republic. It is essentially a slightly creolized hybrid of many English dialects (with a heavy Hiberno-English influence—neither speakers of Irish English nor Newfoundlanders find much of the grammar unfamiliar), and is different enough from other regional English creoles (such as Gullah/Geechee and the general Caribbean pattern) to deserve its own classification.