Subject-matter refers to the theme or the main topic of a discussion or writing. However, sometimes, using the same word repeatedly can get monotonous, and it's best to use synonyms to keep things interesting. Here are a few synonyms of "subject-matter": topic, subject, theme, content, focus, material, message, argument, text, discourse, thesis, point, idea, and issue. These words can be used in place of subject-matter, as they all convey a similar idea. Using synonyms can liven up a piece of writing and make it engaging for the reader. So next time, when you need to convey the subject of your writing, try using one of these synonyms.