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You write

4 + 2 = 6

and say "four plus two equals (or is equal to or is) six."

In the question “Is equal to” or “equals”, I read the following comment:

Equals is equal being a verb, in the present tense. Is equal to is equal being a predicate adjective, with its auxiliary verb in the present tense. English is full of pairs like this, useful if one needs an extra syllable. [...] – John Lawler Jun 16 at 16:18

I am thoroughly confused about the bit "Is equal to is equal being a predicate adjective, with its auxiliary verb in the present tense". Is the verb in the present tense the word is? and is to the predicate with the adjective being equal?

Also, does the word is represent a verb in the present tense in the phrase, "four plus two is six"?

Finally, could you please provide another example that is useful if one needs an extra syllable.

Yes, I understand that they all mean the same thing. What I'm looking for is a grammatical syntax analysis with more examples, since, as John Lawler says, "English is full of pairs like this, useful if one needs an extra syllable."

(As an aside, I once read that this symbol "=" is called an "equals sign" in British English and is called an "equal sign" in American English. A related post can be found here.)

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It appears John Lawler has answered the question adequately at the cited post. You can still post your 'supplementary' questions if any over there. Else this question may be treated as a duplicate. –  Kris Sep 7 '12 at 12:41
Why did you have to choose such a controversial example? ;-) –  SF. Sep 7 '12 at 12:51
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6 Answers

up vote 5 down vote accepted

If one wants a complete grammatical analysis, one should be prepared for the view that be equal to is a transitive multi-word verb, a single lexeme.

("A lexeme is a unit of lexical meaning, which exists regardless of any inflectional endings it may have or the number of words it may contain. Thus, fibrillate, rain cats and dogs, and come in are all lexemes, as are elephant, jog, cholesterol, happiness, put up with, face the music, and hundreds of thousands of other meaningful items in English. The headwords in a dictionary are all lexemes." (David Crystal, The Cambridge Encyclopedia of the English Language, 2nd ed. Cambridge University Press, 2003) )

The fact that is equal to etc can readily be substituted by equals etc strongly supports the multi-word single-lexeme analysis. It then becomes arguable whether it is helpful to try to analyse within the fixed expression (along the lines: is equal more closely bound to the 'verb' or the 'preposition'? if the 'adjective'-'preposition' binding is tight, is to better analysed as a particle?).

Of course, the verb-form is not invariant: So, the left-hand side must be equal to the right-hand side.

Also, be equal to meaning measure up to (the demands of) is not synonymous with equal:

Do you think he is equal to the task?

*Do you think he equals the task?

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Thank you for clarifying and explaining the idea of a "lexeme" as a "single unit of lexical meaning," it is very helpful. –  skullpatrol Sep 20 '12 at 18:14
There is always some room for quibbling on things like this, but if be equal to were a single lexeme, I wouldn’t expect that be would combine with equal to in exactly the same way that it combines with oodles of other adjective phrases (be adjacent to, be reminiscent of). And I wouldn’t expect equal to to work in all the other places where an adjective phrase works (something equal to four, a candidate equal to the challenge). –  Jason Orendorff Sep 20 '12 at 21:06
equal to X can also be modified by all the things that can usually modify an adjective phrase: more or less equal to, precisely equal to, only technically equal to. And you can coordinate equal to with some other adjective: is either negative or equal to zero. All this is evidence that be equal to has grammatical structure. –  Jason Orendorff Sep 20 '12 at 21:26
Crystal claims that 'face the music' is a single lexeme when it is used idiomatically. He would also say that 'music', for instance, is a single lexeme in other usages - ie most of the time. With more complicated examples, as here, I personally am not suggesting that either the 'single lexeme' approach or the 'totally analysable' approach is the right view. –  Edwin Ashworth Sep 24 '12 at 17:01
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The word "equal" has three parts of speech: noun, verb, and adjective.

  1. four plus two equals six

    In your first example sentence, "equal" is being used as a verb in the third person singular form: equals.

  2. four plus two is equal to six

    In your second example, "equal" is being used as an adjective, and so it needs to employ a linking verb (in this case, "be" or "is") before it. The "to" after it is a preposition.

  3. four plus two is six

    Finally, here "is" is again a linking verb in an S + LV + C pattern (Subject + Linking Verb + Complement).

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I'm not entirely sure what the question or questions are, but in the sentence X is equal to Y, is is a lexical, not an auxiliary, verb. Equal is an adjective acting as the subject predicative. To Y is a prepositional phrase acting as the complement to equal.

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My question is about the comment under the first and accepted answer: Equals is equal being a verb, in the present tense. Is equal to is equal being a predicate adjective, with its auxiliary verb in the present tense. English is full of pairs like this, useful if one needs an extra syllable. Could you please provide another example? –  skullpatrol Sep 7 '12 at 11:18
Are you asking if ‘equals’ and ‘is equal to’ mean the same thing? They may mean different things to mathematicians, and on that I cannot comment. In general use, however, they may often mean much the same thing, but can’t always be used in the same context. We can say, for example, ‘He is equal to the task', but we can’t say ‘He equals the task’. –  Barrie England Sep 7 '12 at 11:41
@JohnJunior: I've nothing to add. If you don't understand the answer given in your reference, you should perhaps ask the person who gave it. –  Barrie England Sep 13 '12 at 6:18
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The entire phrase "is equal to" is a predicate, not any part of it. A predicate describes a relationship between two things; in this case, that the first thing ("4 + 2") is related to the second thing ("6") by the first being equal to the second. A predicate describes a static truth, while a verb describes (loosely speaking) an action in progress.

Math makes this distinction especially confusing because math uses practical language to describe abstractions. An example that makes the difference clearer is:

(1) George tends the garden.
(2) George is the tender of the garden.

(1) describes something George does, while (2) describes something George is.

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@John This is straight-up linguistics, not philosophy. The deeper metaphysics of it would be a distracting tangent and isn't what the question is asking about in any case. –  SevenSidedDie Sep 7 '12 at 20:08
How can I get the question moved to the Linguistics stack exchange? –  skullpatrol Sep 7 '12 at 20:12
@John Questions don't get moved because of the analytical tools an answer uses. The question is about English usage and would be OT for the Linguistics Stack, which is for linguistics in itself. Should an answer that uses pictures to explain be moved to Photography.SE? No. –  SevenSidedDie Sep 7 '12 at 20:15
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(bold means a verb, italic means a noun, parentheses mean a prepositional phrase, strikethrough means an adjective).

"Four (plus two) is equal (to six)" N-LV-A
"Four (plus two) is six." N-LV-N
"Four (plus two) equals six". N-LV-N

In the first sentence, "is" is a linking verb or copula. Here "equal" is an adjective, and the predicate of the sentence. The word "six" is the object of the prepositional phrase "to six", which functions as an adverb, modifying the word "equal".

In the second sentence, "is" is still a linking verb, but instead of an adjective, "six" is now the predicate of the sentence, which circumvents the necessity for a prepositional phrase.

Finally, the third sentence does not use "is" at all, but instead uses "equals" as its linking verb. It is more or less identical to the second sentence, but replaces "is" with a more colorful, more descriptive linking verb.

As a somewhat loose follower of the E-Prime philosophy--which in its strictest form mandates the omission of the verb "to be" and all of its conjugations--I would be most inclined to use sentence 3. A quote from the Wikipedia article on the use of "equals" rather than "is":

Replacing statements including "to be" with those using becomes, remains and equals divides perception of, and expressions about, time more operationally into actual cognitive categories that humans know how to act upon.

To claim that one thing equals another is a claim only about the present with no reference to the future or the past—it can be disproved by direct testing.

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Finally, could you please provide another example that is useful if one needs an extra syllable?

Well, it’s actually two syllables –– len(“is equal to”)–len(“equals”) = 4–2 = 2.

An example:

Two bees or not two bees, that is the question;
        To risk a sting to get their sweet confection;
But do not add a dozen to the scene;
        As twelve plus two is equal to fourteen.

Nonsense?  You bet it’s nonsense.  But most modern poetry is –– am I right?

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