Examples of the semantic types:

• Organisms
• Anatomical structures
• Biologic function
• Chemicals
• Events
• Physical objects
• Concepts or ideas

Semantic types are arranged in a hierarchy which is organized into two main categories, Entity and Event.

Examples of Entity semantic types are:

• Amphibian
• Gene or Genome
• Carbohydrate

Examples of Event semantic types are:

• Social Behavior
• Laboratory Procedure
• Mental Process

Semantic types exist in differing levels of granularity or specificity. In the Metathesaurus, semantic type is assigned at the most specific level available. For example, the concept trout would receive the semantic type 'fish', not the semantic type 'animal' because fish is more specific.