Breakdown of Abbiamo festeggiato il diciottesimo compleanno di mio figlio.
avere
to have
il figlio
the son
di
of, from
mio
my
Questions & Answers about Abbiamo festeggiato il diciottesimo compleanno di mio figlio.
How exactly do you form diciottesimo from the number eighteen?
To form ordinal numbers from 11 onwards, you take the regular number, drop its final vowel, and add the suffix -esimo. For eighteen (diciotto), you drop the final -o to get diciott-, then add -esimo to make diciottesimo.
Does diciottesimo change its ending depending on the noun?
Yes. Ordinal numbers ending in -esimo act just like regular adjectives. Because it describes compleanno (a masculine singular noun), it ends in -o. If you were talking about an eighteenth week (settimana), it would become la diciottesima settimana.
Why is there no article before mio figlio? Shouldn't it be del mio figlio?
I have also learned the word celebrare. Why use festeggiare here?