UIFontWeightUltraLight - Ultra thin font
UIFontWeightThin - Thin font
UIFontWeightLight - Light font
UIFontWeightRegular - Regular font
UIFontWeightMedium - between Regular and Semibold
UIFontWeightSemibold - semi-bold font
UIFontWeightBold - Bold font
UIFontWeightHeavy - between Bold and Black
UIFontWeightBlack - Thickest font (understand)