This is the 194th most frequent Catalan word.
avui
"Avui" means "today" in English.
Here, 'avui' is used as an adverb to specify that the action takes place on 'today'.
Avui fa sol i anirem a la platja.
Today it is sunny, and we will go to the beach.
Here, 'avui' emphasizes the occurrence of the event of learning within 'today'.
Avui he aprés una nova paraula en català.
Today, I learned a new word in Catalan.
'Avui' is functioning as a temporal marker distinguishing the current day from future days.