Hádegið — noon, lunch and the daily bath

The three meals

You already know two of them. The middle one completes the set:

hádegið is noon, midday — the middle of the day, around twelve. To say at midday put it in the dative after í: í hádeginu.

Morning as a thing, not a time

morgunninn is the morning as a noun — the thing itself — while á morgnana is the habit, in the mornings.

Bath, swimming, sport

baðið the bath, sundið swimming, íþróttin the sport. Icelanders swim year-round, and fara í sund — to go swimming — is a fixed phrase: you go into swimming, not into a pool.

sofna is to fall asleep — the moment, not the state. Compare sofa, to sleep.