When is a Pig a Hog?: A Guide to Confoundingly Related English Words - Bernice Randall Well it's no wonder foreigners have difficulty with the English language. All in all, a useful book that clarifies some English terms but for the most part it just defines two words that are interchangeable and basically mean the same thing. Will I remember any of this stuff? Probably not but it was interesting to read.

Human & Not So Human Beings was ambiguous at best. Most of the entries didn't clarify anything - one word is basically a synonym for the other while other entries had merit.

Astronaut vs Cosmonaut - A cosmonaut, like an astronaut, is a person trained to make rocket flights in outer space, but he or she is likely to be stationed in the Soviet Union. p23

Judge vs Arbiter - The word judge is not limited to one elected or appointed official with authority to hear and decide cases in a court of law. One of it's other meanings applies to a person whose expert knowledge in a certain field gives him or her the authority to settle controversy or determine the winner of a contest. Arbiter, as applied to a person fully authorized or qualified to judge or decide something, suggests indisputable influence in a particular matter. p22 (sounds like the same thing to me)

Here & There
Capital vs Capitol - A capitAl is a city or town that is the official seat of government of a state or nation. (p48) A capitOl is a building where a legislative body meets. p49

Cape Canaveral vs Cape Kennedy - Cape Canaveral is a proving ground for U.S. missiles and spacecraft. From 1963 to 1973 the Cape was called Cape Kennedy after President John F. Kennedy.

Things
Street vs Avenue - A public thoroughfare in a village, town or city is generally known as a street, particularly if it is paved and has sidewalks and buildings along one or both sides. A broad, principal street is often called an avenue. In many American towns and cities, avenues run at right angles to streets. Who knew a street and an avenue weren't the same thing? Not I.

Concepts, Actions & Intangibles
Part vs Portion vs Piece
A part is any of the components of a whole. A portion is specifically a part allocated to someone. A piece is a part separated from the whole.

Hara-Kiri vs Seppuku - means virtually the same thing. Hara Kiri is literally hara "belly" + kiri "cut" while Seppuku is setsu "cut" + huku "belly".

The Arts - this is not something I care about at all so I just skimmed these 30 pages.

Nature & Science
Here we finally come to an answer for the title.

Pig vs Hog
A pig is an immature swine weighing less than 120 pounds, whereas a hog weighs over 120 pounds.

Our Bodies & Medicine
I always wondered what the difference was between Sadism and Masochism. Well here's the answer... Sadism is getting sexual pleasure from dominating or hurting someone else while Masochism is getting pleasure from being beaten or dominated. Hmm neither one is for me.

Organizations & Institutions
I learned a couple of things, such as the difference between a grand jury (more than 12 people who investigate accusations against people charged with a crime) and a petit jury (less than 12 people who weigh this evidence and decide the outcome of a trial in court). Though most of the remainder was pretty common or common sensical.