Finnish has several morphophonological processes that require modification of the forms of words for daily speech. The most important processes are vowel harmony and consonant gradation.
Vowel harmony is a redundancy feature, which means that the feature [±back] is uniform within a word, and so it is necessary to interpret it only once for a given word. It is meaning-distinguishing in the initial syllable, and suffixes follow; so, if the listener hears [±back] in any part of the word, they can derive [±back] for the initial syllable. For example, tuote (“product”) agglutinates to tuotteeseensa (“into his product”), where the final vowel becomes the back vowel ‘a’ (rather than the front vowel ‘ä’) because the initial syllable contains the back vowels ‘uo’. This is especially notable because vowels ‘a’ and ‘ä’ are different, meaning-distinguishing phonemes, not interchangeable or allophonic. Finnish front vowels are not umlauts.
Consonant gradation is a lenition process for P, T and K, with the oblique stem “weakened” from the nominative stem, or vice versa. For example, tarkka “precise” has the oblique root tarka-, as in tarkan “of the precise”. There is also another gradation pattern, which is older, and causes simple elision of T and K. However, it is very common since it is found in the partitive case marker: if V is a single vowel, V+ta → Va, e.g. *vanha+ta → vanhaa. Another instance is the imperative, which changes into a glottal stop in the singular but is shown as an overt ‘ka’ in plural, e.g. mene vs. menkää.