What is "consonant gradation"

n. (context linguistics English) A type of apophony or mutation of consonants found in Finnic and Sami languages.

Consonant gradation is a type of consonant mutation in which consonants alternate between various "grades". It is typical of Uralic languages such as Finnish, Estonian, Northern Sámi, and the Samoyed language Nganasan. Of the Finnic languages, Votic is known for its extensive set of gradation patterns. Consonant gradation in some of these languages is not (or is no longer) purely phonological although it may be surmised for various reconstructions of Proto-Finnic. In archiphonemic terms, the mutation is a type of lenition in which there are quantitative (such as /kː/ vs. /k/) as well as qualitative (such as /k/ vs. /v/) alternations.

What types of consonants and consonant clusters may undergo gradation vary from language to language; for example, Northern Sámi has three different grades (as well as having three quantities of consonant length), and it also allows for quantitative gradation of its sonorants /l m n r/. Most Finnic languages, however, have two grades and allow only stops to undergo gradation.

Languages may also have other constraints for loanwords; for example, loan words and some personal names in Finnish may have quantitative gradation but not qualitative and so auto does not become *audon '(the) car's' but remains auton.

In addition, the term has been recently used for an unrelated alternation pattern reconstructed for Proto-Germanic, the parent language of the Germanic languages.