Select the most appropriate one-word substitution for the given group of words. 

Living on eating grass and vegetarian only 

Herbivorous

The most appropriate one-word substitution for "living on eating grass and vegetarian only" is herbivorous.

• Piscivorous means eating fish.
• Carnivorous means eating meat.
• Herbivorous means eating plants.
• Glutton means a person who eats too much.

The word herbivorous comes from the Latin words "herba," meaning "grass," and "vorare," meaning "to devour." Herbivorous animals are those that eat plants. Herbivores have a variety of different diets, depending on the type of plant they eat. Some herbivores eat only grasses, while others eat a variety of fruits, vegetables, and nuts.