four
The Italian word 'quattro' is equivalent to the English word 'four'. It is used in the same context you would use the number four in English. Whether you're counting, stating the amount of something, or denoting the position of something, 'quattro' would be your choice in Italian.
I have four cats in my house.
This sentence is stating the number of cats one has at their home. 'Quattro' is used here to specify the quantity. In conjugated Italian sentences, the subject typically comes before the verb.
Four friends decided to take a trip together.
In this sentence, 'quattro' is used to indicate the number of friends who decided to take a trip. Note the use of the verb 'hanno deciso', which means 'they have decided'.
See you at four.
This sentence is an example of how 'quattro' can be used to indicate time. 'Alle quattro' refers to the hour of the day, specifically 4 o'clock.