GMAT Sentence Correction: The Power of “al”, the Adjectival Ending

Fact: the suffix “-al” is one of the standard adjectival ending in English.

A host of complex and interesting adjectives end in “-al”, including adjectival, mercurial, floral, diurnal, banal, nominal, cardinal, terrestrial, vestigial, perennial, and epiphenomenal.  Incidentally, those would all be good words with which to have at least passing familiarity on the GMAT.

Fact: When an adjective ends in “-ic”, the “-al” ending can be added, and usually this doesn’t result in a large change in meaning.  The “-ic” and “ical” forms of the adjective may differ in connotation, in subtle implications, or they may mean exactly the same thing.

For example

  • “electric” and “electrical” both mean “relating to electricity”.  Technically, if the object has electricity running through it — if it operates on electricity — one uses “electric” (i.e. an electric blender, an electric car, etc.); by contrast, if the word pertains to electricity but doesn’t run on electricity, one uses “electrical” (electrical tape, an electrical engineer, etc.)  That subtle difference is highly unlikely to be tested on the GMAT.
  • “comic” and “comical” both mean “causing laughter.”  Technically, the word “comic” is used for works or situations that were intentionally created to be funny, whereas the word “comical” often denotes situations which are unintentionally humorous.  That subtle difference is highly unlikely to be tested on the GMAT.
  • both “ironic” and “ironical” relate to “irony,” itself a word notoriously hard to define precisely.  The difference between “ironic” and “ironical” carries us into some of the most philosophically refined parts of English grammar.  You need not worry about this one on GMAT Sentence Correction.

Fact: Ironically, one “-ic” adjective changes its meaning drastically when “-al” is added — “economic” vs. “economical” — and this one, not surprisingly, runs rife through the Verbal section of the GMAT.

economic — pertaining to the discipline of economics or to the nature of an economy

economical —- saving money; thrifty; giving good value for price

The difference here is stark: in contexts in which one of these is right, the other would be 100% wrong.  Of course, the irony is that this is the GMAT, the test that prepares you for business school, where you will study nothing but economic concerns.  Just by the very nature of the test and its intent, “economic” is one of the most likely adjectives in the English language to appear on the test!  Needless to say, the economic/economical distinction is a favorite of GMAC’s, and economic/economical splits are perhaps my favorite of all possible SC answer choice splits.


Here’s an example from the OG (OG12e, #37; OG 13e, #39):

39) Although shistosomiasis is not often fatal, it is often so debilitating that it has become an economic drain on many developing countries.

      (A) it is often so debilitating that it has become an economic


      (B) it is of such debilitation, it has become an economical


      (C) so debilitating is it as to become an economic


      (D) such is its debilitation, it becomes an economical


    (E) there is so much debilitation that it has become an economical

Let’s start with the split in the final word of the five answer choices: economic vs. economical.  We are talking about the drain that the costs associated with shistosomiasis impose on the economy of a developing country.  In other words, we need an adjective that pertains to a country’s economy: that would be “economic.”  By contrast, an “economical drain” would be a money-saving way to lose money??? That makes no sense!!  Clearly, “economic” is correct and “economical” is completely incorrect: right there you can eliminate (B), (D), and (E), thereby enormously simplifying the task of answering this question.

While we’re discussing this question, I’ll also mention a couple other relevant points.  First of all, “so X that Y” is the correct idiom; “so X as to Y” is incorrect.  That’s why (A) is correct and (C) is incorrect, and this leaves (A) as the only possible correct answer.  Also, notice that the answers flip/flop between “debilitating” (the participle form of a verb) and “debilitation” (a noun).  Which do you think is more active, a noun or a participle?  Verbs are the very essence of action, so any verb form will be more active, more vital, than a static noun.  Strong, direct, active writing is strongly favored on the GMAT.  Therefore, it’s a good bet that if a particular word flip-flops between noun form and verb form among the five answer choices on a GMAT SC question, the correct answer often will involve the verb form, as it does in this question.

Keep an eye out for the economic/economical differences on the GMAT Verbal section and, in cases like the one above, it will be a magic key of simplification.

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  • Mike MᶜGarry

    Mike served as a GMAT Expert at Magoosh, helping create hundreds of lesson videos and practice questions to help guide GMAT students to success. He was also featured as "member of the month" for over two years at GMAT Club. Mike holds an A.B. in Physics (graduating magna cum laude) and an M.T.S. in Religions of the World, both from Harvard. Beyond standardized testing, Mike has over 20 years of both private and public high school teaching experience specializing in math and physics. In his free time, Mike likes smashing foosballs into orbit, and despite having no obvious cranial deficiency, he insists on rooting for the NY Mets. Learn more about the GMAT through Mike's Youtube video explanations and resources like What is a Good GMAT Score? and the GMAT Diagnostic Test.