can you put both singular and plural here?

What I look forward to is/are ( ???) holidays.

And what about: What I like is/are apples?
Thank you very much.

Garzo can give you the correct reasons, but these are examples where it "sounds wrong" to someone, even with good gramnmar.

What I like is is correct.

But, Holidays are what I like.

I would rephrase to: I like apples; I look forward to holidays.  :)

Following gailr examples, I gather that the rules are same as in Spanish… Thus:

The verb must accord with:

1. Pronouns. (I, thou, he, she, we, you, they)
2. Nominal sintagma. (All, Anyone, everyone, somebody, nothing, etc.)
3. Nouns. (Man, cow, horse, etc.)
4. Nominal clauses. (What I heard…, Those who want…, etc.)

When two of equal value are confronted, the one that appears first prevails.

However, I’d wait for Garzo who will certainly know better.

         WS.

Following Brown and Miller (1980), this type of construction - an identity with a nominal relative clause as its subject - is technically a pseudo-cleft sentence. A true cleft sentence has two clauses which can be derived by the cleaving of a single clause. For example, the sentence

  Kasia always votes for the funniest politician in European elections.

Can be turned into the cleft sentences

  1. It is Kasia who always votes for the funniest politician in European elections (Kasia, not anyone else).
  2. It is the funniest politician (that) Kasia always votes for in European elections (not the best-dressed politican).
  3. It is the funniest politician for whom Kasia always votes (as above but playing the not-ending-a-sentence-with-a-preposition game).
  4. It is in European elections that Kasia always votes for the funniest politician (but in Polish elections she does something different).

The pronouns ‘it’ and ‘that’/‘which’/‘who’ are dummy identities that link the two clauses together. The effect is to emphasize one aspect of the original sentence. I’ve added the sense of the emphasis in brackets after each sentence.

The pseudo-cleft structure puts the emphasis at the end of the sentence
 
  What Kasia votes for in European elections is the funniest politician.

Pseudo-clefts can, unlike clefts, emphasize verbs

  What Kasia does in the European elections is (to) vote for the funniest politician.

The two sentences at the top of the thread are

  1. What I look forward to is/are holidays.
  2. What I like is/are apples.

Clefts, and pseudo-clefts, are about emphasis. There is very little in either of these sentences that needs emphasis: ‘holidays’ and ‘apples’ are the obvious candidates for emphasis. This type of construction would only occur as part of a larger discussion about looking forward to things, or liking things.

The two sides of the sentence have to agree in number (singular or plural), and the form of the verb ‘be’ used as copula marks this out. The easy answer is that ‘holidays’ and ‘apples’ are both plurals, and demand a plural copula

  1. What I look forward to are holidays.
  2. What I like are apples.

It is possible to think of ‘what’ as standing for ‘the thing that’, singular. It goes with a plural object because it is emphasizing that it isn’t the concept of holiday that is looked forward to, nor a particular apple that is liked.

  1. What I look forward to is holiday.
  2. What I look forward to is apples.

I don’t really like the sentence (2), although it is correct if ‘what’ is singular. However, ‘holidays’ can be thought of as an uncount noun with plural form. This is particularly the case when it has the definite article - ‘the holidays’ - referring to a period of time, singular.

  What I look forward to every year is the holidays.

Strict grammars would mark this usage as wrong, but it emphasizes the difference between ‘holiday’ the concept, and ‘holidays’ the period of time.

  What I look forward to every year is holiday.

At first sight, pseudo-clefts look ugly. That’s because they need to form part of a wider discussion of the unemphasized element.

  This summer, Basia looks forward to writing the great Polish novel, but what Kasia looks forward to is holidays.

- What Garzo.
I apologize for overusing your name - I hope I didn’t wear it out.

Thanks Garzo—I learned something here, as well.

I thought my grammar was Right and Good, having learned it from Dominican nuns and all. But I don’t remember any lectures and diagrams on cleavage (psuedo or genuine) or copula (singular, let alone ... J-M-&-J! ... plural). Can’t imagine why not…

gailr
who should probably go do some sort of penance for joking about both nuns and grammar

When it comes to [sic] grammer, cleave unto Garzo.

Perry

PS:  I am just sic over my typo.

[quote author=gailr link=board=grammar;num=1087235237;start=0#4 date=06/15/04 at 00:39:45]
or copula (singular, let alone ... J-M-&-J! ... plural). Can’t imagine why not…

who should probably go do some sort of penance for joking about both nuns and grammar

As far as copula verbs are concerned, back in the old days, we were taught that they required a "subjective completion". These days the young whippersnappers who wrote the textbooks for the ESL courses I teach call copula verbs "joining verbs" and say nothing about the subjective completion. Of course this is purely subjective.
I suppose I’m dating myself, too, but sometimes that can be the best alternative to what’s out there!