Written material and Written communication

Written material noun - The work of a writer; anything expressed in letters of the alphabet (especially when considered from the point of view of style and effect).

Written communication and written material are semantically related. In some cases you can use "Written communication" instead a noun phrase "Written material".

Written communication noun - Communication by means of written symbols (either printed or handwritten).

Written material and written communication are semantically related. Sometimes you can replace phrase "Written material" with "Written communication", this phrases are similar.