Text height determines the size in drawing units of the letters in the font you are using. Except in TrueType fonts, the value usually represents the size of the uppercase letters.
If you specify a fixed height as part of a text style, AutoCAD LT bypasses the Height prompt when you create single-line text. When the height is set to 0 in the text style, AutoCAD LT prompts for the height each time you create single-line text. Set the value to 0 if you want to specify the height as you create text.
For TrueType fonts, the value specified for text height represents the height of a capital letter plus an ascent area reserved for accent marks and other marks used in non-English languages. The relative portion of text height that is assigned to capital letters and ascent characters is determined by the font designer at the time the font is designed; consequently, it varies from font to font.
In addition to the height of a capital letter and the ascent area that make up the text height specified by the user, TrueType fonts have a descent area for portions of characters that extend below the text insertion line, for example, y, j, p, g, and q.