"They do not know what they are missing."

Translation: Loro non sanno cosa si stanno perdendo.

[Armusj]

I used 'mancando' instead of 'perdendo' and got rejected. Why? Please comment on difference in meaning of mancare and perdere wrt sense of 'missing' intended in this sentence.

[Marees]

why is this si stanno? is it wrong to not use the reflexive? Ie non sanno cosa stanno perdendo?

[johnrush]

I also do not understand why 'si stanno perdendo' is used. According to wordreference, perdersi means to 'get lost' or 'lose one's way'. See http://www.wordreference.com/iten/perdere.

Probably si is used because this is si impersonale construction, with the impersonal or undefined subject 'si': what one is missing, 'si sta perdendo'; what you are missing, 'si sta perdendo'; what they are missing, 'si stanno perdendo'.

[jgbachand]

My question, too. When I look up "miss" in the dictionary, it gives "perdere" without the reflexive. (The "hover hints" are useless for suggesting the use of "si"). "Si" seems to come out of the blue, so to speak.

[coloraday]

perdersi qualcosa = to miss something

[sfoehner]

Can this be considered correct? "Non sanno ciò che stanno perdendo."