Bar Above in Word 2013

If you're using the built-in equation editor (Alt+= or Insert > Equation > New Equation), you'll find the item you want in the Accent gallery of the Equation Tools ribbon:

The length of the bar will automatically expand as you type characters into the placeholder box:

You're describing either a macro or a vinculum. A macron is a diacritic ¯ placed over a vowel. It is usually used in pronunciation guides as an indication that the vowel has a long sound. A vinculum is a bar ¯ placed over any letter or number. It is used in mathematical notation, most commonly to indicate a repeating decimal. Some fonts support macrons, but others do not. Strictly speaking, none support vinculums. The following descriptions show ways of producing a diacritic over any letter usin field coding, and can thus be used for macrons and vinculums alike:

• use a field coded as {EQ \x\to(a)}. This solution increases the vertical spacing for the affected line (which you could get around by reducing the field’s point size).

• use a field coded as {EQ \o (-,a)}. To achieve the desired result, superscript the first character in the field and subscript the second character, which leads to small characters for both (which you could counter by increasing the point size), but this too increases the vertical spacing for the affected line … Note: if you have more than one subscripted character, you’ll need to compensate by increasing the # of superscripted characters and there’ll invariably be gaps between them.

• use a field coded as {EQ \s\up6(\f(,a))}. Compared to the other solutions, this one has the advantage of retaining the character sizes without increasing the line height. The ‘6’ in the formula controls the bar height.

In each example, replace the ‘a’ in the field with the desired character(s).

Note: The field brace pairs (i.e. '{ }') for the above example are all created in the document itself, via Ctrl-F9 (Cmd-F9 on a Mac); you can't simply type them or copy & paste them from this message. Nor is it practical to add them via any of the standard Word dialogues.