Chapter I: The Long Vowels and Diphthongs

=3.= The long vowels are always shortened when followed by =i=, that is to say, the vowel is written once and not twice. Thus =maa=, _earth_, which takes an =i= in all the cases in the plural except the nominative, forms =maita=, =maitten=, =maiksi=, etc., not =maaita=; =puu=, _tree_, =puita=, =puiden=, =puiksi=.

=4.= The diphthongs with the accent on the second vowel, =uo=, =yö=, =ie=, when followed by =i=, reject the first vowel, and thus form a new diphthong—=työ=, _work_, becomes in the plural =töistä=, =töissä=, =töiksi=, etc.; =vien=, _I lead_, =vein= (=vie-in=), _I led_; =luo=, _he creates_, =loisi= (=luo-isi=), _he would create_.

=5.= Diphthongs ending in =i= reject this =i= if another =i= follows, =uin=, _I swim_, =uin= (for =ui-in=), _I swam_.

In the root =käy=, _to go_, =y= is changed into =v= before a vowel—e.g. =käy-in= becomes =kävin=.