How to use 'of'

There are three main uses of 'of'.
  • Quantitative 'of' is used with measure words (e.g. a bottle of water and two meters of rope). 
  • Possessive 'of' is used for possession (e.g. the dog's tail --> the tail of the dog).
  • Descriptive 'of' is used to specify the noun (e.g. the joy of motherhood and the joy of traveling).
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How to know which is which. For 'the city of London', we can ask the following questions.
  • Can we say two cities of London? No. London is not something that can be divided into measurable units. (not quantitative)
  • Can we say London has a city? No. London can possess things (e.g. London has a flag and London has a GDP), but London does not own another city. (not possessive)
  • Can we ask what city? Yes, and the answer is London. (descriptive) Other examples include...
    • ​A height of 10 meters --> What height? 10 meters
    • A map of the city --> What map? A map of the city (since a city is more than a map, the answer cannot simply be 'the city')
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A common issue with 'of' is using two or more to construct a phrase, which can make your writing unclear/confusing (e.g. several of the books of an author of unknown nationality). If you are faced with this issue, you should (in the following order) either:
  • ​Change the possessive 'of'
    • Move the second noun to the front and add a possessive 's'.
      • The battery of my phone --> My phone's battery
  • Use another preposition
    • If possible.
      • Redness of the lips --> Redness in the lips
  • ​Change the descriptive 'of'
    • Move the second noun to the front and change it to singular.
      • ​Infestations of mites --> Mite infestations