Subject alignment

Semantic subject - grammatical subject

The semantic subject of a discourse is the main topic or the central idea being discussed. The grammatical subject of a sentence is the part of the sentence that performs the action. 

To identify the grammatical subject, you diagram the sentence and its parts of speech. Diagramming is also known as parsing, and it looks something like this: 

When these two align, it means that the main topic of your discussion is also the entity performing the action in your sentences.

In simple terms, is the thing you are talking about the first thing to appear in your sentence? 

 If not, why not? (You may have a good reason).

Aligning the semantic subject with the grammatical subject enhances the clarity of your writing by keeping the reader's attention on the most important person, thing or concept.

In simple terms, put the important thing first and make sure it takes a verb that makes sense.