// using custom fonts
label.font = UIFont(name: "fontname", size: 50)
// using system fonts
label.font = UIFont.systemFont(ofSize: 20.0)
label.font = UIFont.boldSystemFont(ofSize: 20.0)
label.font = UIFont.italicSystemFont(ofSize: 20.0)
// modifying only the font size
label.font = label.font.withSize(20)
// adjusting the font size within the label width
label.adjustsFontSizeToFitWidth = true