A compound word is two words put together to make a new word. In English there are thousands of compound nouns, so it is good to know a few basic things about them.
Compound noun spelling
The first thing to know is that some compound nouns are written with one word (closed compounds), such as “sunset”, and some are written with two separate words (open compounds), such as “sun tan”. There are also a few that are hyphenated, which means they are connected with a dash mark, such as “sun-belt”.
Here are a few more examples:
Closed compound nouns: network, snowfall, notebook, offspring, fishbowl, laptop, nonsense.
Open compound nouns: apple tree, ski pole, music stand, graph paper, chalk board, rush hour, turtle shell.
Hyphenated compound nouns: get-together, check-in, in-laws, close-up.
By the way, these sometimes change over time — some words that are written as an open compound today, might be written as a single word in 10 years from now. Also, some are spelled more than one way, such as half-sister / half sister, or even all three ways, such as lifestyle / life-style / life style.
What that means, is that you can not always recognize a compound noun just by seeing it. However, you can identify a compound noun by listening to the stress.
Compound noun stress
The stress pattern of compound nouns is staightforward — the first word has stronger stress. This is true whether the compound noun is closed or open. In fact, the stress pattern makes open compounds sound like one word, even though they are spelled as two words.
Listen to the stress of these compound nouns — they all have the same stress pattern. In fact, if you listen with your eyes closed, you might not know which ones are open or closed: daylight, coat room, bookworm, yard sale, pathway, oil change, volleyball, flower bed, chestnut, light year.
There are some words that really seem like they should be a compound noun, but they are not, such as: “iced tea”, “apple pie” (all types of pie), and “fast food”. So the best strategy is to use regular compound noun stress when you think that it is a compound, but always be ready to switch the stress if it seems like there is some misunderstanding. So for example, if you go to a restaurant and ask for “LEMON pie” but they don’t know what you are saying, then swtich the stress and say it again “lemon PIE”.
Compound nouns are everywhere – keep your eye open for them, or rather, your ear open for them.