The Options menu of most programs contains a "Set fonts" command. This brings up a font selection dialogue consisting of some sample text, three option menus to select the font name, family and size, and some check buttons for font styles.
In the above picture, button_font is the currently selected font name. This option menu contains several of the following font types. The exact ones available depends on the program being used.
Next to the font name is the font family selector. The contents of this menu will depend on the fonts available to your system. Some may be inappropriate, or not even in the correct language. Next to the family selector is the size menu. This contains a range of sizes in both pixel and point units. If a font of a particular size is not available, the nearest font or size will be automatically chosen. Specifying fonts to be a fixed number of points states that the font should have a specific physical size, regardless of monitor size or screen resolution. There are 72.27 points to the inch. Underneath these we have Bold, Italic, Overstrike and Underline check buttons.
Whilst choosing the font, the fonts used in the entire program automatically update to show you how things will look. Pressing "Cancel" will reset the fonts back to their original state. Pressing "OK" will keep these chosen fonts, until the program is exited. Pressing "OK Permanent" will keep these fonts, but will also add them to the user's `$HOME/.tk_utilsrc' file. This file is processed when the programs start up, and so your font choice will be permanently chosen. To remove this font choice, manual editing of the `$HOME/.tk_utilsrc' file is required.