Dialectal - dialectical
This seems to confuse the issue. Where there are two separate nouns, there are two meanings; and where there are two meanings, it seems useful to have two distinct adjectives. So this article is designed to maintain a difference which - in all likelihood - is doomed.
- 'Dialect' is a word used about language. It means 'a variety of a language'. (See also dialect.) This is usually the variety found in a particular geographical area: e.g., Cockney is the dialect of London. In the 16th and 17th centuries, it was used to mean what we now call dialectic - but this is obsolete.
- 'Dialectic' is a word most useful in talking about ideas - in the subjects of Philosophy, Politics, History and so on. It means 'a system of discussion', or 'a way of arguing logically'. It was originally 'Question and Answer'; it has come to mean more 'progressing by opposites'. For a better understanding, you will have to see a good Philosophy textbook.
- ('The Dialectic' is a term often used to mean the system of studying History taught by Karl Marx, and derived by him from the German philosopher Hegel.)
AWE recommends you to write with academic precision. Keep dialectal to refer to linguistic matters - 'to do with dialect'. Keep dialectical to refer to Logic and argument - 'to do with dialectic'.
- The confusion is not recent. Fowler (1996) reports that in the nineteenth century dialect and dialectal "were freely used in the sense 'belonging to or of the nature of a dialect', but the only one now used in this sense in professional work is dialectal."