Insects (Class Insecta) are a major group of arthropods and the most diverse group of animals on the Earth, with over a million described species - more than half of all known living organisms - with estimates of undescribed species as high as 30 million, thus potentially representing over 90% of the differing life forms on the planet. Insects may be found in nearly all environments on the planet, although only a small number of species occur in the oceans.
The study of insects (from Latin insectus, meaning "cut into sections") is called entomology, from the Greek εντομον, also meaning "cut into sections".