Etymology (explaining the origin of the word itself)
History (if relevant, discussing the history of the term/its use/controversies associated with it)
Cause and effect (discussing how the situation came about and what effects it may have)
Description (how a term or phrase defined looks like visually and anatomically)
Principles of operation (discussing how topic in a statement or question functions, including any special materials or conditions required)
Classification (showing how the topic fits into a larger category)
Contrast/Negation (showing how the topic differs from others in the same class)
Comparison (showing how the topic is similar to others in the class)
Analogy (explaining by comparing two dissimilar topics, where the second is familiar to the audience)
Examples (providing examples to the word being described gives extended meaning)
Illustration (provide a picture or images that is used to clarify a text)