* No clear-cut definition: There's no universally agreed upon definition of what constitutes a "major" dialect. This depends on how you're measuring dialectal variation (e.g., phonology, vocabulary, grammar, regional distribution, social prestige).
* Continuum, not categories: Dialect variation exists on a spectrum, not in distinct, separated categories. It's more accurate to talk about dialect regions with gradual transitions between them.
* Overlapping boundaries: Dialect regions often overlap, making it hard to define where one stops and another begins.
However, linguists often identify major dialect regions in the US:
* Northern: Includes New England, New York City, parts of the Great Lakes region, and the upper Midwest.
* Midland: Encompasses the Ohio Valley, the Great Plains, and parts of the South.
* Southern: Extends from Virginia and North Carolina to Texas and Florida.
* Western: Covers the Pacific Coast, including California, Oregon, and Washington.
Within these regions, there are further sub-dialects and variations. For example, within the South, you'll find distinctive dialects in Appalachian regions, the Deep South, and the Coastal South.
In conclusion, there's no single, universally agreed upon number of "major" US dialects. It's more accurate to acknowledge the existence of dialect regions with overlapping boundaries and gradual transitions in linguistic features.