方言学是对语言差异的研究。狭义的方言学指的是对地域性语言差异的研究，又称为方言地理学。广义的方言学包含对地域性语言差异和社会性语言差异的研究，则与社会语言学有密切的关系。

Dialectology (from Greek διάλεκτος, dialektos, "talk, dialect"; and -λογία, -logia) is the scientific study of linguistic dialect, a sub-field of sociolinguistics. It studies variations in language based primarily on geographic distribution and their associated features. Dialectology treats such topics as divergence of two local dialects from a common ancestor and synchronic variation.