Abbrev.From 'app' to 'math': abbreviating words is human. Why write words in full if a shorter version will do? Medieval scribes agreed. The manuscripts they made are usually packed with abbreviations. Perhaps the most common is the macron: a line above a letter that represents the letter n or m. In this image the first (Latin) word reads "omnia" (all), but the scribe wrote "omia" with a line over the letter i.