Several character classes do not typically or cannot wear armor. Sorcerer, Monk, Wizard, Barbarian. Monk, Barbarian, and even draconian ancestry sorcerer have unarmored defense perks that help boost their AC. But Wizard does not. So what is the wizards unarmored AC?
I suspect it is 10 as everything seems to add to that value in the armor table and in the unarmored defense (except draconian ancestry which seems to give +3 for scales). But I have not been able to find that rule in the PHB.