Because it is one of many kinds of food.

@Rathony: More specifically, it is a kind of bread.

Biscuits is a kind of cake. It means twice cooked.

Because of the law of conservation of mass nouns, which states that no matter how much energy you apply to a mass noun, you can't change it into a countable noun, only into another mass noun. Thus bread is a mass noun, and if you apply heat to it you convert it into toast, which by the law, remains a mass noun.

You don't toast an entire loaf of bread.

Bread belongs to food. This question is too broad. That's what I meant, @sumelic.

Mari-LouA: what kind of answer would be satisfying here? It seems to me that to get a good explanation, you'd need to get into pretty complicated linguistic theories (that may not even be fully developed). [Or go the facetious route, as deadrat is doing]

@Rathony: How is it too broad? It's literally about a single word. A question about the countability of food terms in general would be too broad.

Bread is bread, no matter how you slice it. The energy applied to the knife in slicing a loaf of bread won't change the bread into a countable noun.

@sumelic Now, you want to discuss "broadness" of this question. Just because it is about a single word, it doesn't make this question "not broad". If I could ask "why is "grain" uncountable?" how many questions do you think I could post here.

I'm voting to close this question as off-topic because not only is the question too broad to answer, but also answers could be many depending on various points of view.

Grain has both countable and noncountable uses. The former because there are different types of grain: "This field is planted in a grain; that one, in a legume." But although we have been given pictures of different types of toast, it's still a mass noun only. @Mari-LouA, can you add a picture of French toast?

Hate to break it to you, but it's not at all uncommon to hear "two toasts" in the US. And sometimes that's even while having breakfast.

@HotLicks That's what I wanted to mention in the previous comment.

@HotLicks: that's a more general phenomenon, though: pretty much all "uncountable" nouns are able to be pluralized like this (compare to two waters). If this disqualifies "toast" from being called uncountable, what can be called uncountable?

If toast was countable, what would we be counting? The slices of toast or the loafs of toast?

All I know is that after the 3rd or 4th toast I lose count.

If I'm in a restaurant with my family and ordering Sunday lunch, I'm likely to say "That will be 2 beefs, 2 lambs and 1 pork please". But that doesn't mean that "beef", "lamb" and "pork" should be reclassified as countable nouns.

Isn't that a sandwich (prepared with toasted bread) which we erroneously call a toast?

I'm asking why "toast" is uncountable when obviously you can count it.

@HotLicks great, Americans tend to be more practical on these matters, their spelling is more sensible, and they feel freer to exploit the language for their needs. Post an answer repeating your comment, and it's one deserved upvote from me, and probably several others.

@Josh61 yes, wasn't my explanation clear? I've also highlighted the fact that in Italian, "tost" or "toast" is countable.

This is a great question. Anything that helps us understand our language better!

I mean, isn't "toasted bread " as uncountable as "bread" is? , a toast is just a short for "a sandwich prepared with toasted bread" in the same way as "a water" can be the the short for "a bottle of water".

@Mari-LouA Sure, but in making the sandwich, you've not only supplied the energy to make it, you've contaminated it with other nouns, so the conservation law doesn't apply, even if you cut the crusts off. Off the sandwich, not the law. But if you know why bread is noncountable, don't you per force know why toast is as well?

@deadrat - yes, that's it.

@deadrat why not post an answer then? You've explained it in the comments, and we all know comments get deleted for one reason or the other.

@Mari-LouA Are you asking me to put the Conservation of Mass Nouns Law in an answer? (He asked, hoping for an answer in the negative.)

To the person who VTC this question for lack of research, I defy you to find a link that answers my question in the first two pages. Why is toast uncountable"? Same words but muddled to increase the number of results. Typing the exact expression ,word to word, has only 13 hits.

A toast to this question! And I call for more toasts so that we can count them!

You know, sometimes the answer (especially in this forum) is "It is what it is." There is no "logic" to many things in English. It is largely the result of Brownian motion and, were the clock somehow wound back and it done all over again, many things would be completely different.

@sumelic (comment 5 at my time of writing) Usages. The concept is valid and useful; it's naive to expect all nouns to have solely count or mass usages. Most 'mass nouns' (those which were once solely non-count) are countified, so it becomes a senseless classification for nouns.

@Mari-LouA - At breakfast you don't like to strain your brain.

Oops .. All OED entries have 'toast' countable. Very strange to my ears - because I never pluralise it and know no-one who does! c1430 Two Cookery-bks. (E.E.T.S.) 12 Oyle Soppys...caste þer-to Safroune, ...an serue forth alle hote as tostes. 1655 J. Howell 4th Vol. Familiar Lett. xli. 96 This drink..must be attended with a brown tost. 1838 Dickens Let. 1 Feb. (1965) I. 366 We have had for breakfast, toasts, cakes, ... 1978 Vishveshvaranand Indological Jrnl. 16 218 He had stopped taking cereals ... but ...had to re-start on medical advice taking two toasts or some cornflakes.

The OED has two 'toasts'. The first (older) is 'put in wine, water, or other beverage' and is countable. This usage is rare or obsolete except in India. The uncountable usage is first recorded (OED) around 1735 - Swift Panegyrick on D— in Wks. II. 294 Sweeten your Tea, and watch your Toast. Also 1885 J. Ruskin Præterita I. iii. 84 Quarrelling with her which should have the brownest bits of toast.

The history of how 'toast' is uncountable is followable (there are instances mentioned here where it is not, but most instances (in the expected meaning) are uncountable. 'Why' may be difficult to substantiate other than an explanation by analogy with other uncountable situations. It does seem weird since you'd think that pieces of toast should be called 'toast' plain and simple. Why it is not is I think just 'because'.

@Bill Johnstone Classifying nouns which exhibit both types of behaviour as either 'countable or 'mass/uncountable' is poor analysis. It's usages that are count or otherwise (or sometimes apparently halfway between: a gentle light suffused the scene / two gentle lights ...). // OED apparently labels *toast 'countable'; I'd prefer separate entries (or at least 'noncount and count') under the same headword.Some dictionaries show this level of sophistication.

@EdwinAshworth - OED gives two 'toasts' - the older, countable, used with drinks and now with strongly regional usage, and the more recent (1735), uncountable, current usage.

I wasn't implying otherwise Edwin; the point I was making was that we use the terms countable or uncountable for their predominant use, so I would not expect the "beef" in "Can I have 2 beefs and 1 pork please?" to be listed as a countable noun. If a noun can freely be used both ways, then dictionaries will cite both, though with some nouns consistency is patchy. For example, the basic Cambridge online dictionary gives "toast" (the food) only as uncountable, whereas the Oxford gives it as uncountable, except for "stilton and pear toasts" which it correctly says is countable.

@Dan How does that allow your 'Oops .. All OED entries have 'toast' countable.'?

@Bill I'd agree that it makes sense to concede that idiomaticity trumps avoidance of inflationary use of terms when using non-technical registers. But saying 'sea is a mass noun' is like saying 'run is an intransitive verb'.

There are other examples where resistance to countification-for-discrete-portions-of is seen: rock (as in Blackpool); bitter, mild (beer); meat etc; cheese and cake have count versions, but not for individual helpings (except for small entire servings). Chocolate is very peculiar; the count noun sense is subtly different semantically, perhaps being derived from chocolate confection.

Toasters don't toast toast toast toast toast.

When I worked the county fair as a teenager and someone would order, for example, "2 corns" instead of "2 cobs (of corn)" I always shuddered at the thought of delivering pieces of hardened skin cut from someone's foot...

Related: Why is bread uncountable? How do you describe the “three breads” in the picture?

@deadrat I said you should have posted an answer, 33 people agree with your comment. And if the comments, one day, get deleted. or this question gets closed, there are three VTC so far.

Mari-Lou, we've actually been pulling your leg all along. The term for a slice of bread which has been browned on both sides is not "toast", it's "lobster".

Why are grapes uncountable in Italian?

@Kundor this is an English language website, my Italian example is showing how Italians consider tost or toast countable. As for grapes, well in Italian the individual ....grape, is called chicco d'uva, and so you can ask for tre chicchi and receive three individual grapes. Or you could just use the countable word, acino, which means chicco d'uva (a single grape)

But obviously you can count grapes. And everything you say about "chicco" applies equally well to "slice". The point is that there is very little rhyme or reason to these things. As with prepositions in different languages, it's bootless to ask why.

@Kundor On the contrary, I don't think my question is pointless, it's rather interesting and curious. A slice of toast is not the same as a cut slice of bread. the food today is called toast, not "toasted sliced bread" or "toasted pieces of bread", perhaps it was called that in the past before it became a stable feature on British breakfast tables, perhaps that is the key.

If you can count pancakes, although they are made from an uncountable mass substance called batter, why can't you count "toasts", why hasn't it become countable?

You may find the following interesting : TLFi with the reference to the Bath, Sommerset anecdote, and DmF for the tostee. In Fr this is countable (that I know of), will even take the mark of the plural (toasts), but should always be pronounced like the singular (toast/toste). It's all quite interesting. Thanks!

@deadrat: As much as I like the rule, using google I found a countable bread, which breaks the theory: amazon.ca/Bernard-Claytons-Complete-Small-Breads/dp/0684826925 It looks like small breads is a widely used phrase, another example: sailusfood.com/2008/07/11/….

@deadrat Until it becomes ashes...

I don't usually have many disagreements with Downing and Locke (English Grammar: A University Course' [2006]) but I think their 'Note that toast meaning 'toasted bread' is always non-count and requires 'a piece [etc] of' in order to refer to an individuated piece' is outdated (though reflected on many grammar sites and in several dictionaries). I'd say that countification (of the bread sense) (and according to Uri's update, that should be recountification) is progressing increasingly quickly today.

I wish I was more of an expert but, ironically, I am not.

I'd add to the previous comment that the other common type of countification process, to the 'varieties of' ('arabica and robusta coffees are the two most commonly used'; contrast 'two coffees to go, please'), is clearly in use: {laweekly.com} '10 Best Classic French Toasts in Los Angeles'. This article also contains the noncount usage, and, arguably, the slice-count usage.

@RobAu ... still noncountable

@Mari-LouA The first result in the google for "pancake batters" turns up "Shop for pancake batters on Google." When you make pancakes, you only use one batter, namely the one you just mixed up.

@Neolisk Bread turns countable when modified -- sweet breads, altar breads, and as you found, small breads. But if you toast small breads, you still don't get small toasts. I'll have to ponder the implications for the theory.

I believe I've never seen such a long string of comments that didn't get shoved into a chat room.  I mention that because I got exhausted from reading them, and so, if the following point was already made, I missed it.  … … … … … … … … … … … … …  @Mari-LouA: You can manage to count most forms of matter: pieces of wood, grains of sand, buckets of dirt, even pounds (or kilograms) of oxygen.  That doesn't change the fact that the words themselves — wood, sand, dirt, air, and elements such as oxygen, hydrogen, iodine, iron, mercury, nitrogen, etc. — are uncountable.

@deadrat: I'm intrigued by the law of conservation of mass nouns, but I question it.  If you apply energy to pieces of cookie dough, you get cookies, and if you apply energy to coal, you get embers.

@Scott Pieces of cookie dough is countable, so the law doesn't apply. If you apply energy to coal, you get clinker. Neither one of us is using emoticons, and at least one of us should be. It won't be me -- I'm too old.

@Mari-Lou A: Counting pancakes: You can count pancakes because the batter has been quantized. This is elementary quantum mechanics.

@Scott Certain usages of at least two of the nouns you mention (wood, sand) are count (without going to distant senses, like No 4 wood or in the woods): 'different woods have very different properties' / 'the sands of time are running out'.

@Scott and this is what happens when you get such a long trail of comments. Sigh... some comments were really good though.

@deadrat see, I told you so!! Please post an answer, it's a shame that your comment will be lost forever....

@EdwinAshworth am I allowed to pick and choose the best comments from the bunch and ask the mods to reinstall them back to the OP?

I'm sifting through the comments, and I shall be posting an answer...

Sorry, M-L, I'm not the person to ask. I avoid politics (though do my fair share of policing). Overall, I think that Mitch's response comes closest to answering 'Why [has the count usage been so rare]?' (ie 'unknown'), but your question gets nice answers to 'Why was it largely used as a mass noun?' / 'Has it been used as a count noun before the 1980s say?' and a reasonable one to 'Where is the count usage on the acceptability scale now?'

@Mari-LouA: It won't be lost forever: there are enough posts here for this room to continue existing indefinitely.

@deadrat "Because of the law of conservation of mass nouns, which states that no matter how much energy you apply to a mass noun, you can't change it into a countable noun" Except when you convert some chicken (or, if you prefer, some mechanically recovered meat) into a dozen chicken nuggets.