Types of apposition
In writing, we often separate the noun phrases by commas. We do this when the second noun phrase gives extra information which is not necessary to identify the person or thing:
Edinburgh, Scotland’s capital city, has a population of around 450,000. (Scotland’s capital city is extra information which is not necessary to identify Edinburgh.)
Sometimes the second noun phrase contains information which specifies which person or thing we are referring to from a number of possible people or things. In these cases, we don’t use a comma.
commas | no commas |
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