Besides these simple and double vowels there are also 16 diphthongs, in which both vowels should be sounded but so rapidly and continuously as to form one syllable. They may be divided into two classes.
(1) Those in which the stress is on the second vowel. uo, yö, ie, e.g. tuo, this, tie, a way, yö, night.
(2) Those in which the stress is on the first vowel. Of these there are—
(a) Four ending in u. au, ou, iu, eu. Kauppa, sale, koulu, school, hiukka, a grain, leuka, chin.
(b) Two ending in y: äy, öy. Väylä, river bed, höyhen, feather.
(c) Seven ending in i: ai, oi, ui, ei, äi, öi, yi. E.g. nai, he married, koi, a moth, pui, he threshed, vei, he led, päivä, day, löi, he struck, myi, he sold.
These diphthongs, with the exception of those ending in i, are found only in the first syllable of words, otherwise the two vowels form two syllables: e.g. tapa-us, not tapa͡us, kope-us, not kope͡us, but talko͡issa, pape͡illa.
The pronunciation of these diphthongs offers no difficulties when that of the simple vowels has been mastered. It must be remembered that they are real diphthongs where both vowels sounds are heard, but pronounced rapidly, so that au, though very near the ow in the English how, is not quite like it. The pronunciation of äy and öy requires attention, but is, like that of all the diphthongs, merely the result of pronouncing the simple vowels rapidly.
The chief accent in Finnish is always on the first syllable of every word. Tálo, mínä, párempi, kívettä.