Question

Fish-
Amphibian-
Mammal-
Magma-
Lava-
Earthquake-
Tectonic Plates-
Ring of Fire-
Tsunami-
Tide-
Could you please give me the definitions in science terms?

Answer 1

FYI: For fish, from the linked-to site, use 2 of the defintions:

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1. Any of numerous cold-blooded aquatic vertebrates of the superclass Pisces, characteristically having fins, gills, and a streamlined body and including specifically:

a. Any of the class Osteichthyes, having a bony skeleton.

b. Any of the class Chondrichthyes, having a cartilaginous skeleton and including the sharks, rays, and skates.

...

3. Any of various primitive aquatic vertebrates of the class Cyclostomata, lacking jaws and including the lampreys and hagfishes.
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And do not use

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4. Any of various unrelated aquatic animals, such as a jellyfish, cuttlefish, or crayfish.
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They are not fish.

Answer 2

And if you are allowed to define something by including in the definition what it is not, then for an amphibian I'd define it as

amphibian: a non-amniote tetrapod.