i think that's because "aspetta" is forma di cortesia. When you want to speak politely in italian, you use this form and instead of putting the verb in the second person singular you put it in the third person singular, that's why is "aspetta" (lui/lei) and not "aspetti" (tu).
Kallistheni is right, the polite form in Italian is always lui/lei (dependent on the gender of the person you're talking to). When you want to form an imperative form, such as "do!", "look!" or "listen!", you use the 2nd person singular if you want to make it informal ("fai!" = "do!"), and the 3rd person singular if you want to make it formal ("fa!" = "do!"). Same counts for the sentence "how are you?", which can be "come stai?", but also "come sta?". If you've read this well, you can see which of these is formal and which is informal ;)
Actually it's not that simple. Imperatives of regular -are verbs like aspettare work in reverse for 2nd and 3rd person singular:
- tu aspett
- lui/lei/Lei aspett
Irregular verbs like fare have their own conjugations:
- tu fa
- lui/lei/Lei f
Thus, the "fa" form is used similarly to regular -are verbs, while the "fai" form is used similarly to regular -ere or -ire verbs (the same form for 2nd person singular indicative and imperative)
When you say it to someone as an order/wish its imperative tense not present tense.
Tu aspetti (a statement) Tu aspetta! (I'm ordering you to follow this command)
The conjugations for imperative are almost identical to present except that third person and second person endings are switched. First person however remains the same so that "Noi aspettiamo" can mean both "Let's wait" (an order) and "We wait" (a statement)
So if I am thinking correctly, some verbs in Italian in their present form can also be understood as if they were a present progressive? Ex. We wait and we are waiting. But, there is also a present progressive form in Italian using essere? Ex. sono mangiate - I am eating. Io sono vero?
While reading this, a general question popped up in my mind - how often do most people, I wonder, use the hint when they have forgotten a word, do most people guess? I feel a little uncomfortable hinting sometimes, like I'm not putting in enough effort; still that's what hints are for I guess. Just wondered how other people on here approach them.
I use it when I want to know other possible meanings of a word, but not when I don't know the word at all. In case I don't know the word I just type in everything else, leave out the unknown word and hit Enter to read the correction. This way I get my 'hint' and can try again a few questions later without cheating. And I also find out if the rest of the sentence was correct.