When we talk about the "main focus" of something, we are referring to its primary or central point of attention. However, there are several other words and phrases that can be used to convey a similar meaning. For example, we could refer to the "core objective", "primary goal", "main purpose" or "central theme" of a project or task. Similarly, we could talk about the "key element", "central point", "primary concern" or "core focus" of a particular discussion or argument. Ultimately, the choice of synonym will depend on the context and tone of the communication, but each of these words and phrases can help to convey a clear and concise message about the main idea or focus of the topic at hand.