dialect vs subdialect

dialect

noun
  • A variety of a language that is characteristic of a particular area, community, or social group, differing from other varieties of the same language in relatively minor ways as regards grammar, phonology, and lexicon. 

  • A language existing only in an oral or non-standardized form, especially a language spoken in a developing country or an isolated region. 

  • A variant form of the vocalizations of a bird species restricted to a certain area or population. 

  • A variant of a non-standardized programming language. 

  • Language that is perceived as substandard or wrong. 

  • A lect (often a regional or minority language) as part of a group or family of languages, especially if they are viewed as a single language, or if contrasted with a standardized idiom that is considered the 'true' form of the language (for example, Cantonese as contrasted with Mandarin Chinese or Bavarian as contrasted with Standard German). 

subdialect

noun
  • A subdivision of a dialect 

How often have the words dialect and subdialect occurred in a corpus of books? (source: Google Ngram Viewer )