BBC English Learning Compoung words Lyrics
Your question, Charles, touches on an important process in forming words in English, a process that we call compounding. What happens is that two independent words combine and make one compound word.
Many compounds are spelled as one word - as in the two words that you mentioned: classroom and blackboard. But there are many compound words that are not spelled as one word, but that are spelled with a hyphen. And in many cases some people will spell them one way, and others will spell them another way - so eye-witness with a hyphen can be spelled eyewitness without a hyphen; the same is true of drop-out. You can see it written in both ways (drop-out or dropout). Other compounds are always written as two different words - like petrol station or heart attack.
There are two rules that can help - or maybe I should call these generalisations rather than rules. Let's look at some words that are compounded and written as one word: blackbird; whiteboard; bathroom; skateboard; greenhouse. Observe how many syllables they have - they have two syllables, and each of the independent words that make them up is one syllable.
On the other hand, compounds where one of the words has more than one syllable are normally written with a hyphen or as two separate words. So bathroom is one word; but living room is written as two words. Blackboard is one word, but drawing board is written as two words.
The second important rule concerns the stress. Teachers always like to talk about the difference between a blackbird, which is a compound that refers to a specific kind of bird, and a black bird, which is any bird that is black, and is not a compound. Or about a greenhouse - a glass building where you grow plants, which is a compound - and a green house, which is a house that is green - and is not a compound.
You will notice that in these short compounds, made of two words of one syllable, the first syllable is stressed, and this is always true. This is also true for most longer compounds - not all, but most of them - so, for example, we talk about a petrol station, not a petrol station; or a heart attack, not a heart attack.
So, to sum up, I have made two generalisations about compounds, and this may help you. But there is really no substitute for a good dictionary in this case, because these rules are not fixed!
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