Summary dialect and varieties

A dialect is a regional or social variety of a language distinguished bypronunciation, grammar, and/orvocabulary. Adjective: dialectal.

The term dialect is often used to characterize a way of speaking that differs from the standard variety of the language. Nonetheless, as David Crystal explains below, "Everyone speaks a dialect."

The scientific study of dialects is known as dialectology, commonly regarded as a subfield of sociolinguistics.

What's the Difference Between a Language and a Dialect?
"The very fact that 'language' and 'dialect' persist as separate concepts implies that linguists can make tidy distinctions for speech varieties worldwide. But in fact, there is no objective difference between the two: Any attempt you make to impose that kind of order on reality falls apart in the face of real evidence. . . .

"English tempts one with a tidy dialect-language distinction based on 'intelligibility': If you can understand it without training, it’s a dialect of your own language; if you can’t, it’s a different language. But because of quirks of its history, English happens to lack very close relatives, and the intelligibility standard doesn’t apply consistently beyond it. . . .

What's the Difference Between a Dialect and an Accent?
"Accents have to be distinguished from dialects. An accent is a person's distinctive pronunciation. A dialect is a much broader notion: it refers to the distinctive vocabulary and grammar of someone's use of language. If you say eether and I sayiyther, that's accent. We use the same word but pronounce it differently. But if you say I've got a new dustbin and I say I've gotten a new garbage can, that's dialect. We're using different word and sentence patterns to talk about the same thing."