While text labels and buttons usually contain a single line of text, Tkinter also supports multiple lines. To split the text across lines, simply insert newline characters (\n) where necessary.
By default, the lines are centered. You can change this by setting the justify option to LEFT or RIGHT. The default value is CENTER.
You can also use the wraplength option to set a maximum width, and let the widget wrap the text over multiple lines all by itself. Tkinter attempts to wrap on whitespace, but if the widget is too narrow, it may break individual words across lines.