Readability is defined as the degree of difficulty of the message.  These items contribute to greater reading difficulty:

• Long sentences
• Words with several syllables
• Technical terms

Readability formulas, such as the Gunning Fog Index and the Flesch-Kincaid Index provide readability indices.  The higher the readability index, the less readable the message.  There are many online websites that will give you readability calculators to check the readability index of your work (http://simbon.madpage.com/Fog/).

You can  check your readability by using the built-in function from Word.  If you go to the Options section under Proofing, under the section “When correcting spelling and grammar in Word”, select the “Show readability statistics”. The statistics will appear every time you run a spell and grammar check.