Dialect
Linguistic distance

An important criterion for categorizing varieties of language is linguistic distance. For a variety to be considered a dialect, the linguistic distance between the two varieties must be low. Linguistic distance between spoken or written forms of language increases as the differences between the forms are characterized. For example, two languages with completely different syntactical structures would have a high linguistic distance, while a language with very few differences from another may be considered a dialect or a sibling of that language. Linguistic distance may be used to determine language families and language siblings. For example, languages with little linguistic distance, like Dutch and German, are considered siblings. Dutch and German are siblings in the West-Germanic language group. Some language siblings are closer to each other in terms of linguistic distance than to other linguistic siblings. French and Spanish, siblings in the Romance Branch of the Indo-European group, are closer to each other than they are to any of the languages of the West-Germanic group. When languages are close in terms of linguistic distance, they resemble one another, hence why dialects are not considered linguistically distant to their parent language.
oulipo:avoid_letter[e], change_case:english_lowercase