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What Are Relative Adverbs? (with Examples)

What Are Relative Adverbs? (with Examples)

The relative adverbs are where, when, and why. A relative adverb is an adverb that introduces an adjective clause. Each one has its own role:
  • Where is an adverb of place.
  • When is an adverb of time.
  • Why is an adverb of reason.
A relative adverb is used to start a description for a noun. (This description is called an adjective clause.) For example:
  • The seat where we sat last Saturday is still free.
  • (The noun is the seat. The relative adverb is where. The adjective clause identifying the seat is shaded.)

  • I can remember a time when I could eat four hamburgers.
  • (The noun being identified is a time.)

  • We do not know the reason why he left..
  • (The noun being identified is the reason.)
    (When the relative adverb why modifies reason, you can omit the word reason to avoid a tautology, i.e., unnecessary repetition.)
  • We do not know why he left.
Note: When a noun like seat has accompanying modifiers (here, the seat), it is known as a noun phrase.

When To Use a Comma before a Relative Adverb

In each of the examples above, the adjective clause (shaded) identifies the noun. When this happens, it is known as a restrictive clause, and it is not offset with commas (i.e., there is no comma before the relative adverb). Occasionally, however, the clause headed by a relative adverb just gives us some additional information. When this happens, it is known as a non-restrictive clause, and it is offset with commas. For example:
  • Let's sit on this seat, where we'll get splashed.
  • (The noun phrase is this seat. (Note that it is already identified.) The relative adverb is where. The adjective clause (shaded) is not identifying the seat. It is just providing some additional information, which is why there is a comma before where.)

  • I can remember my nineteenth birthday, when I had long hair.
  • (The noun phrase is my nineteenth birthday. (Note that it is already identified.) The relative adverb is when. The adjective clause (shaded) is not identifying my nineteenth birthday. It is just providing some additional information, which is why there is a comma before when.)
Non-restrictive clauses are far more common with relative pronouns (e.g., that, which, who) than with relative adverbs.
Note

You Can Often Replace a Relative Adverb with a Preposition and Which

A relative adverb can nearly always be replaced with a preposition and the relative pronoun which. For example:
  • I am parked near the pier where we caught the conger eel.
  • I am parked near the pier on which we caught the conger eel.

  • I remember the era when teachers could give students the cane.
  • I remember the era during which teachers could give students the cane.

  • Tell us the reason why you ditched your tent.
  • Tell us the reason for which you ditched your tent.
  • (This example is shown for completeness. Remember, with reason why, you should delete one of the words to avoid a tautology.)
Of note, some people still consider the "[preposition] + which" versions to be more formal. This view is outdated in our opinion. To the modern ear, these versions sound awkward.