Readability is the degree to which prose can be understood, determined by word length, word commonality, sentence length, number of clauses in a sentence and the number of syllables in the sentence. It is something that is often overlooked by designers and researchers, who often believe that more complex information requires complex presentation. This, of course, is bunkum. The principle of cognitive fluency teaches us that the easier something is to read the more readily it will be understood and the more likely it will be acted on. I write this as I am preparing for a client workshop on report writing where the number 1 principle is make everything as simple as possible (but no simpler as Einstein famously said).The first step to readability is to omit all the words and phrases which are unnecessary to communicating the core meaning that you want to convey. Of course, this should not compromise clarity or meaning, but it is often very easy to take out a large amount of verbal clutter without changing your message. Likewise, although it is often tempting to do so, leave out technical jargon, acronyms and foreign language quotations 9unless you explain them). Sentence length should be appropriate to the target audience, but generally shorter is better. Active voices are more appropriate in most situations unless the emphasis is on the message rather than the messenger.
There are a wide range of formulas for producing text with specific readability levels, and the most commonly used is Edward Fry’s Readability Graph, relating sentence length and number of syllables to reading age or grade. Other tools generally use similar approaches. These formulas can be used to ensure that text is matched to the abilities of the target audience, but there are other considerations and simplicity is not a bad thing ever for more advanced audience, as long as it is not so simple that it obscures the intended meaning.
Any design or any communication that involves prose should concern itself with readability. Even the most complex material can always be presented in simpler ways that help convey the meaning but are accessible across the widest possible audience..
Universal Principles of Design by Lidwell, Holden & Butler
The Elements of Style by Strunk & White