Regarding attributes of fonts in Microsoft Word or any other application, each font set has several variations. For example, if you select a font – “Arial” and click on the Bold button, the font is replaced by another font variation “Arial Bold.” If you click on Italics as well, you reach the third font variation that is both bold and italic. Thus, for a single font “Arial,” there are four font variations installed on your computer – “Arial standard,” “Arial Bold,” “Arial Italic,” and “Arial Bold Italic.” Based upon your selection, Microsoft Word replaces the highlighted portion with one of the above variations for the font set. The following images help you understand the different font variations for a single font set.

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Among other attributes of the font is its size. However, there are no different font variations for different font sizes. The same variation is used to display fonts of different sizes. You also see options such as shadow, strikeout, shimmer, etc. when you open the font dialog box (CTRL +D in Microsoft Word). These are features specific to the application and font sets do not need carry definitions for these options.
In short, only the typefaces – normal, bold, italic and bold-italic – are created with any font so that users can format them. Size, shadows, shimmering, etc. are not included in the font definitions and are features specific to Microsoft Word. Sometimes you may see that a particular formatting is absent (e.g., you cannot bold a few fonts). If the formatting feature is not available in the font dialog, it means there is no variation for that particular font set. For more on font attributes, please read our article Font Types You Should Know.