Although the LSAT does not explicitly test your vocabulary, you will encounter some words / phrases that you may only have a partial understanding of. While practicing on former LSAT tests, look up the exact definitions of words that you do not know or are unsure of. Here are some common terms / phrases that trip up LSAT test-takers:
"After all" – This phrase signifies an additional premium after the conclusion has already been stated. Thus, read "After all" as "Because". Be wary of this phrase when it appears in a main point question introducing the final sentence to a paragraph because it introduces an additional premise, not the author's conclusion. See LSAT PrepTest 49, Section 4, Question 16 for an example.
"unique" – In conversation, the term "unique" is often used as a combination of "interesting", "different", "neat", "creative", and "quirky". However, the word "unique" simply means the only one of its kind.
"viable" – You will see this used in two slightly different ways. First, you will see it used to mean "possible", such as a "viable alternative". Second, you will see this used to mean "live-capable", such as in a passage with science content that discusses what percentage of a species' offspring are "viable."
"afford" – Often in conversation, this word reiter to financial concerns. However, "afford" does not always refer to financial concerns; afford can refer to time, effort, or other factors. See LSAT PrepTest 49, Section 4, Question 21, Choice (C) for an example.
"truth", "true", "correct", "in fact", "prove" – Often in conversation, these terms are used to emphasize opinions, tastes, preferences. However, on the LSAT, if an author states that something is "true", then that author believes that the information's correctness is beyond dispute – no opinions allowed. See LSAT PrepTest 48, Section 1, Question 3 and LSAT PrepTest 48, Section 4, Question 4 for examples. Likewise, terms such as "wrong", "incorrect", "false", or "disprove" means that the author believes that something is indisputably wrong. See the conclusion of LSAT PrepTest 50, Section 4, Question 17.
"fail" – This is an extreme statement that something has not worked out at all. If a plan has partially succeeded, then it does not count as having failed. See (C) on LSAT PrepTest 50, Section 4, Question 20.
"same" – In conversation, this is often used as a synonym for similar, but an important distinction exists between the two. It's easy to forget to apply the exact definition of the word on the LSAT – remember that "same" means that all details are exactly the same between two things. If only one tiny detail is just a little bit different in one thing, then the adjective "similar" applies. See (A) on LSAT PrepTest 48, Section 4, Question 22.
"evidence" – This is often used to mean specific facts – numbers, dates, experiments – to indisputably prove a point. However, the LSAT may use this to simply mean a promise in support of a conclusion.