A Heading 2 can be used for the various main sections of the document - similar to chapter titles in a book. Heading 3 elements can be used for sub-sections contained within a Heading 2 section.

X Chapter Title X.1 Main Section Heading X.1.1 Sub Section Heading X.1.1.1 Lower Sub Section Heading * Books in the Issues in Environmental Science and Technology series do not have chapter numbers.

In APA format there are five levels of headings that create degrees of importance in relation to each other. Basically, they just function like a bulleted list, with each new level meaning you’re ...