ocean v. sea

71% of the Earth’s surface is covered with a continuous body of saltwater that has been divided into five sections: the Pacific, Atlantic, Indian, Southern, and Arctic Oceans.

A sea is either a part of the ocean bordering land, or a huge saline lake. Seas can be largely unbounded, like the Arabian Sea, mostly encircled by continents or islands, like the Caribbean Sea, or completely enclosed and isolated from the ocean, like the Caspian Sea. There are over 100 seas in the world.

A NASA satellite photo of the Aegean Sea.

cougar v. puma v. mountain lion v. panther v. catamount

A mountain lion (or cougar, or puma, or panther, or catamount) leaping. Cougar, puma, and mountain lion are all names for the same species of large, tawny cat (Puma concolor) found throughout North and South America.

The terms panther and catamount are somewhat ambiguous. A panther can be any of several big cats, especially if they are black. In the Americas, panther can refer to either a cougar or a jaguar (Panthera onca). In Africa and Asia, a panther is a leopard (Panthera pardus). A catamount is either a cougar or a lynx.

poison v. toxin v. venom

Yellow-banded poison dart frog. Image courtesy of Audubon Magazine. A poison is any substance that causes injury, disease, or death through chemical means when ingested, inhaled, or otherwise absorbed into the body. Household cleaners, medicine, pesticides, gasoline, and certain plants and animals can all be poisonous.

Toxins are poisons produced by living organisms (e.g., animals, plants, fungi, and bacteria), and may be used for defense or predation.

Venom is a type of toxin secreted by some animals (such as spiders, wasps, snakes, and fish) that is injected into victims by stinging or biting. 

• The term poisonous is applied to organisms that are harmful when touched or eaten, and the term venomous is reserved for animals that deliver their toxins by biting or stinging.
• If an animal is poisonous, its entire body (or large parts of it) will contain poison. Venom is only found in specialized venom glands.
• Poisonous organisms usually use their poison defensively, to avoid being eaten; venomous animals can use their venom to immobilize pray, or as a defense mechanism.
• While poison is harmful if consumed, venom usually isn’t.

PreserveVenomous.com on venom v. poison

insect v. bug

A giant water bug. Image courtesy of The Ranger’s Blog. True bugs are insects belonging to the order Hemiptera, such as aphids, leafhoppers, shield bugs, bed bugs, and cicadas. Hemipterans are characterized by the presence of elongated mouthparts used for piercing tissue and sucking fluids. In addition, their forewings are generally thick at the base and membranous at the tip, and they typically have five-segmented antennae and three-segmented tarsi.

Colloquially, bug can refer to most terrestrial arthropods (e.g., other insects, spiders, centipedes) or to bacteria.

BugGuide.net on Hemiptera

llama v. alpaca v. guanaco v. vicuña

The lamoids are a group of South American camelids comprising llamas, alpacas, guanacos, and vicuñas. Llamas and alpacas are domestic and have thick coats in a variety of colors. Guanacos and vicuñas are wild. They are light brown with white underneath.

The llama (Lama glama) is a pack animal that is also used for fiber and meat. Llamas are about 1.1 meters tall at the withers, and are descended from guanacos.

A llama, mugging for the camera above Machu Picchu.

Alpacas (Vicugna pacos), which are descended from vicuñas, are smaller than llamas, standing about 0.9 meters at the withers. Compared to llamas, they have shorter heads and shorter, straighter ears. Alpacas also have a thick tuft of fur on top of the head, which is usually absent in llamas. Alpacas are too small to be used as pack animals. Instead, they are bred for their warm, soft, silky fleece, which is finer than llama fiber.

Four alpacas (left) and a llama (right).

Just as alpacas look somewhat like small llamas, vicuñas (Vicugna vicugna) look like small, thin guanacos (Lama guanicoe).

A guanaco.

Vicuñas.

eHow on llama v. alpaca