One absolutely frightening thing about Gaelic is that when you think you know a word, suddenly that word appears looking very very different leaving the reader very very confused. Some of these differences we have already spoken about, like an H coming in after the first letter, or an I being added at the end (lenition and slenderisation).
In Slenderisation particularly, when the I is added, another vowel letter sometimes changes. This happens a lot, but today we want to focus on short nouns because these usually change when they are in the possessive.
Try to examine the following and complete the ones which are missing:
Ceann becomes cinn / mo chinn / my head
fear becomes fir / còta an fhir mhòir / coat of the big man
mac becomes mic / ainm a mic / name of her son
falt becomes fuilt
eun becomes eòin
bard becomes bhùird
Please see page 32 of Gràmar na Gàidhlig by MIchael Byrne