Consistent headings. Look for the most succinct and informative way to word headings. In general, state a topic in a single word, usually a noun (Toxicity); in a phrase, usually a noun phrase (Levels of Toxicity) or a gerund phrase (Measuring Toxicity); in a question that will be answered in the text (How Can Toxicity Be Measured?); or in an imperative that tells readers what steps to take (Measure the Toxicity). Whichever structure you choose, make sure you use it consistently for all headings of the same level.