Armor Class
Source Player Core pg. 244
Your Armor Class (AC) measures how well you can defend against attacks. When a creature attacks you, your Armor Class is the DC for that attack roll.
Use your proficiency bonus for the category (light, medium, or heavy) or the specific type of armor you're wearing. If you're not wearing armor, use your proficiency in unarmored defense.
Use your proficiency bonus for the category (light, medium, or heavy) or the specific type of armor you're wearing. If you're not wearing armor, use your proficiency in unarmored defense.