Kingdom - The highest classification into which living organisms are grouped. One widely accepted system of classification divides life into five kingdoms: prokaryotes, protists, fungi, plants, and animals.

Animal - A multicellular organism of the kingdom Animalia.

Mammal   - Warm-blooded vertebrate animals. This includes humans. They have hair on the skin, and the females produce milk for their young.

Fish - Any of numerous cold-blooded vertebrate animals that live in water. Fish have gills for obtaining oxygen.

Invertebrate  -   Having no backbone or spinal column.
 

Fungus   - Any eukaryotic organisms of the kingdom Fungi. They do not have chlorophyll or vascular tissue. The kingdom includes the yeasts, molds, smuts, and mushrooms.

Plant  - Living organisms that make their own food. Most of them have chlorophyll.

Protist  - Any of a group of eukaryotic organisms belonging to the kingdom Protista. The protists include protozoans, slime molds, brown algae, and red algae.

Vertebrate - having vertebrae, a backbone, or a spinal column.

Classification - Putting things into classes or categories of the same type.

Some of these definitions are taken from http://www.dictionary.com.