the best thing to do is (to) concentrate on

Question

The best thing to do is to concentrate on something else.

I've known in the sentence like that 'to' should be omitted. So, I wonder if the sentence is grammatical.

*The source of the information was some English test prep book. According to it, in case the subjective involves "do" and the verb is "be", the complement should be "infinitive" without 'to'.

Well, now I guess it doesn't need to omit 'to', though.

What is the source of your information? Why did you consider credible? Always try to cite a reference. — Kris, Feb 03 '13 at 10:23
Welcome to EL&U. Off topic (proofreading request). Please recast as a general question. Thanks. — MetaEd, Feb 03 '13 at 14:18
There are two complementizer to's in your sentence. The first one (the one introducing the relative infinitive to do is not dispensible; it is required to mark the relative infinitive. The second one (the one introducing the infinitive to concentrate) is dispensible, since NP complementizers are normally only required when they begin the sentence; they're optional elsewhere. — John Lawler, Feb 03 '13 at 17:42
Related: “All you have to do is read” vs. “All you have to do is to read” — RegDwigнt, Jun 03 '14 at 17:30

score 5 · Answer 1 · answered Feb 03 '13 at 09:22

5

It can be omitted, but there is no should about it.

answered Feb 03 '13 at 09:22

Barrie England

140,205

Blessed Geek · Answer 2 · 2013-02-03T11:51:53.437

If we are to follow usual conventions of English grammar, the preposition "to" should not be omitted. The reason is as following ...

He has {to go to school}.

He has {going to school as a necessity}.

He has {necessity of going to school}.

i.e., He has {complex noun}.
His responsibility is {to go to school}.

His responsibility is {going to school}.

i.e., His responsibility is {complex noun}.

By complex noun, I meant either

a simple noun with or without adjectival modifiers
His responsibility is {a new school).
prepositional phrase
His responsibility is {of the school)
relative wh-clause (what, who, where, etc
His responsibility is {which girl he likes}
infinitive phrase
His responsibility is {to go to school}
present-participle/gerund phrase
His responsibility is {going to school)
coupled predicate
His responsibility is {that going to school is enjoyable)
modified complex noun
His responsibility is {largely that of going to school is enjoyable)

Therefore, saying

The best thing to do is {concentrate on something}

is akin to saying

His responsibility is {go to school}

which is a poorly written sentence because {go to school} does not fit as a complex noun phrase. It is a verb-phrase.

If you wish to drop the preposition, you would need to turn it into a gerund phrase

The best thing to do is {concentrating on something}

The phenomenon of dropping the preposition of an infinitive phrase is a misjudgment practiced by iphone/android-texting kids, and often overlooked by their grammatical guardians when the verb in the infinitive phrase is longer than two syllables.

the best thing to do is (to) concentrate on

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