verbs Y: * yell * yammer * yank * yawn * yearn * yield (to produce a result)
When a suffix is added to a word ending in a consonant the y changes to an I.
yummy
Anatomy, archery
yacketyyak
bravery
actually activity acrimony
balcony
ApologyOthers include:abilityacidityactuaryagilityallergyamenityamiablyanalogyanatomyanchovyangrilyanomalyatrophy
custody calumny
Yule and yoke
How about "density"?
kinky, kooky, Kentucky, kidney, key