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

  1. Swetha February 28, 2014 at 3:24 am #

    Hi Mike,

    With regards to the OG example you explained above, I am wondering why you instantly crossed (C) as incorrect.

    I see it of the form: SO [Adjective] AS TO Infinitive phrase but with a flipped subject-verb.
    ie, it is so debilitating as to become -> so debilitating is it as to become.

    It sure sounds odd as hell, but so do a few of the correct GMAT SC answers, so I’m trying to not rule out anything just based on its oddness. For this question per se, there is nothing wrong with (A) so I would definitely go with it if I were to answer it on the GMAT; but I want to be clarified of what’s exactly wrong with (C).

    Thanks in advance.
    Kind regards,

    • Mike MᶜGarry
      Mike February 28, 2014 at 11:29 am #

      Dear Swetha,
      I’m happy to respond. Yes, (C) is grammatically correct. First of all, (C) lacks the information about verb tense that (A) contains —- choice (A) correctly has the present perfect. letting us know that this has been going on and still is going on. Choice (A) leaves everything about time ambiguous — is this current? future? What does it “become”? Furthermore, the construction in choice (C) would be appropriate if we wanted to emphasize the adjective — “so offensive were his comments that I ….” Here, the adjective “debilitating” does not merit any special singling out. Therefore, the connotations of (C) are not appropriate to the sentence. In the absence of wanting to stress these connotations, (C) is just unnecessarily indirect, and for that reason, it wouldn’t be acceptable.
      Does all this make sense?
      Mike 🙂

      • Sweatha February 28, 2014 at 10:03 pm #

        Very much. Thanks again for your explaination, Mike!

        • Mike MᶜGarry
          Mike March 1, 2014 at 8:12 pm #

          Dear Sweatha,
          You are quite welcome, my friend. Best of luck to you!
          Mike 🙂

  2. Vijay December 3, 2013 at 8:13 pm #

    Hi Mike,
    But the first one have the Subject – verb pair error. Isn’t it?
    “that is”. According to my understanding “That” is not playing as a subject. It is a being used as conjuction and starting of restrictive clause. But for the second clause there is no subject.


    • Mike MᶜGarry
      Mike December 4, 2013 at 10:14 am #

      There was a simple typo which I just corrected. This should resolve the issue.
      Mike 🙂

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