What's the difference between dialect and accent?

A common mistake is to confuse a dialect with an accent , muddling up the difference between words people use and the sounds they make, their pronunciation. If vocabulary and grammar are being considered alongside pronunciation, then ‘dialect’ is a reasonable term to use. But often, when claiming to discuss a dialect, someone will concentrate just on pronunciations. If what is being spoken about are sounds alone—that is, accent—then the area of language study is rather pronunciation, or phonology .

Accent, or pronunciation, is a special element of a dialect that needs separate attention to be properly understood. A famous distinction in pronunciation in England is the so-called ‘BATH vowel’, the quality of the ‘a’ sound differing between north and south. For example, someone from Leeds, in the north of England, would typically pronounce ‘bath’ with the short ‘a’ of ‘cat’, whereas someone from Oxford, in the south of England, would typically pronounce ‘bath’ with the long ‘a’ of ‘father’. Another distinction, still more significant on the world stage, concerns the issue of  rhoticity, i.e. whether or not a written ‘r’ is sounded when it follows a vowel, for example in the words ‘car’ and ‘butter’. Whilst most people in England and Wales do not pronounce the ‘r’ (and are therefore  non- rhotic), many in South-West England and parts of Lancashire do. In this they are joined by most Scots and Irish speakers of English, and by the majority of North Americans. Rhoticity is in fact numerically and geographically the dominant form in world terms.

Dialect 

A dialect is a variety of language differing in vocabulary and gramma as well as pronunciation . Dialects are usually spoken by a group united by geography or class.

Accent 

When a standard language and pronunciation are defined by a group, an accent may be any pronunciation that deviates from that standard. 

References:

www.voxforge.org/home/docs/faq/faq/what-is-the-difference-between-a-dialect-and-an-accent

www.oxforddictionaries.com/words/what-is-the-difference-between-dialect-and-accent