Table of Mutations
Note that 'g' always becomes silent when it is softened. If the 'g' is an afficative, pronounced like the 'j' in jam, as before the vowels 'i' and 'e', then the 'g' is not softened. Likewise 'c' before a front vowel becomes 'g', with the j-pronunciation when it is softened. 'C' before 'i' or 'e' does not undergo spirant mutation, but may soften in those circumstances.
What causes mutations? Mutations are caused by the loss of sounds at the end of preceding words. A word ending in a vowel, such as the -a ending of feminine article, noun, or adjective causes the next word to soften. For the most part these vowels have been lost, except in a few one-syllabled words, such as pronouns, articles and prepositions. (Note that the Romance masculine ending -o had been lost before this softening started to take place.) Spirant mutations are caused by an original -s on the end of words that became -h before it vanished but still affects following words.
The exception to this rule is the preposition a from latin `ad', where the final -d became assimilated in sound with the consonant following it, and then the cluster underwent spirant mutation. In the modern language this rule has become irregular and dropped. Before a vowel the preposition a and the conjunction e are more likely to add the ending -dd, becoming a-dd and e-dd.
Nasal mutation is caused by nasal consonant ending the preposition, or the lost negative participle `non'. Even though the -n or -m is still written, it is pronounced the same as the nasal mutation following it.