between voiced and voiceless fricatives partly phonemicized (largely due to the influx of French loanwords), the alternation was morphologized. Examples English In Old English, velar stops were palatalized in certain cases but not others. That resulted in some alternations, many of which have been levelled, but traces occur in some word doublets such as ditch and dike . In the past tense of certain verbs, English also retains traces of several ancient sound developments such as *kt > *xt and *ŋx > *x; many of them have been further complicated by the loss of in the Middle English. seek : sought think : thought The pair teach : taught has a combination of both this and palatalization. A second palatalization, called yod-coalescence, occurs in loanwords from Latin. One subtype affects the sibilant consonants: earlier and were palatalized, leading to an alternation between alveolar and postalveolar . confess : confession fuse : fusion Another unproductive layer results from the Vulgar Latin palatalization of velar stops before front vowels. It is thus imported from the Romance languages, and alternate with . induce : induction magic : magus A combination of inherited and loaned alternation also occurs: an alternation pattern *t : *sj was brought over in Latinate loanwords, which in English was then turned into an alternation between and . act : action Celtic languages The Celtic languages are well-known for their initial consonant mutations. The individual languages vary on the number of mutations available: Scottish Gaelic has one, Irish and Manx have two, Welsh, Cornish and Breton have four (if mixed mutations are counted). Cornish and Breton have so-called mixed mutations; a trigger causes one mutation to some sounds and another to other sounds. Welsh also has a mixed mutation (triggered by na, ni and oni). The languages vary on the environments for the mutations, but some generalizations can be made. Those languages all have feminine singular nouns mutated after the definite article, with adjectives mutated after feminine singular nouns. In most of the languages, the possessive determiners trigger various mutations. Here are some examples from Breton, Irish, Scottish Gaelic, and Welsh: Older textbooks on Gaelic sometimes refer to the c → ch mutation as "aspiration", but it is not aspiration in the sense of the word used by modern phoneticians, and linguists prefer to speak of lenition here. Historically, the Celtic initial mutations originated from progressive assimilation and sandhi phenomena