It is common for fonts intended for use in books for young children to use simplified, 'single-storey' forms of the lowercase letters a and g (sometimes also y and l ); these may be called infant or schoolbook alternates. They are traditionally believed to be easier for children to read and less confusing as they resemble the forms used in handwriting.  Often schoolbook characters are released as a supplement to popular families such as Akzidenz-Grotesk , Gill Sans and Bembo ; a well-known font intended specifically for school use is Sassoon Sans .  
The standard unit for measuring type size is the point . A point is 1 ⁄ 72 of an inch, roughly one pixel on a computer screen. The point size of a font tells you the size of the “em square” in which your computer displays each letter of the typeface. How tall or wide any given letter is depends on how the type designer drew it within the em square, thus a font’s height and width can vary greatly depending on the design of the typeface. That’s why if you set two fonts at the same point size, one usually looks bigger than the other.