Always write in plain language. If possible, use words that are part of common usage – recognisable words help understanding.
Use short sentences where possible – aim for an average sentence length of 15 to 20 words. Even when communicating complex information, try and break up long sentences. If you need to use multiple clauses in a sentence, make sure it's properly punctuated to orientate the reader.
The Readability Guidelines are a useful resource for creating inclusive content that caters for people with diverse needs.