For vs. Of

for and of

First, a summary of when to use the prepositions “for” and “of”. “For” is usually used to indicate the recipient, purpose or reason of an action, while “of” is often used to give information related to something. For example, “of” can express attributes or possession between things. In addition, both “for” and “of” can be used to talk about time, but in different ways.

Listen to the first set of examples. Both sentences are about a necklace and use “for” and “of” respectively, but their meanings are completely different.

(Recipient)

• Was this necklace made for me?
  (Was this necklace made especially for me?)

• Is this necklace made of gold?
  (Is this necklace made from gold?)

(Purpose)

• How many grams of soybeans do we need to make tofu? We need thirty grams for tofu.
  (How many grams of soybeans are needed to make tofu? Thirty grams of soybeans are needed for the tofu.)

• We need thirty grams of tofu.
  (Thirty grams of tofu are needed.)

In the first example, “We need thirty grams for tofu.” means “we need thirty grams of soybeans to make tofu”. Here, “for” indicates purpose. In the second example, “We need thirty grams of tofu.” means “we need thirty grams of tofu itself”; “of” has nothing to do with purpose here and names the thing being measured.

• This is the house for our clients.
  (This is the house prepared for our clients.) The preposition “for” indicates the use or purpose of the house

• This is the house of our clients.
  (This is the house that belongs to our clients.) Here, “of” indicates possession.

(Reason)

• She won an award for her brilliant performance.
  (She received an award because her performance was brilliant.)

• She won an award of £1000.
  (She received prize money of £1000.)

Both “for” and “of” can be used to talk about time, but in different ways. With time, “for” usually indicates how long something lasts, while “of” tends to introduce what the activity lasting that time is. Listen to the fifth set of examples.

• I had to listen to him for two hours!
  (I was forced to listen to him talk for two hours!)

• I had to listen to two hours of him speaking!
  (I was forced to listen to him talk for two hours!)

Both sentences mean “I had to listen to him talk for two hours”, but they use “for” and “of” respectively. In the first sentence, “listen to him for two hours”, “for” indicates how long the act of listening lasted. In the second, “listen to two hours of him speaking”, “of” introduces what exactly those two hours of listening consisted of.

notes

In general, “for” indicates the recipient, purpose or reason of an action, while “of” gives information related to something, such as attributes or possession. When talking about time, “for” usually indicates how long an action lasts, while “of” explains what the action specifically is. It is worth listening to the examples again to consolidate your understanding of the two words.