Instead, my antenna picks up messages sent by humans back in the United States.

The sentence should look like

Instead, my antenna picks up messages which are sent by humans back in the United State.

My question is, why is "which are" taken away?

  • 3
    Simply because those words are unnecessary. The meaning is perfectly clear without them. You could ask why the sentence doesn't say, "Instead, my antenna picks up messages sent by humans who are back in the United States." Keep it pithy! May 25 at 0:45

2 Answers 2


It's called relative clause reduction (which is a fancy way of saying what @Old Brixtonian commented). See the answers to this question.

But you asked why it's being done here. I think there are two possible reasons. The first is simply one of preferred style. As @Old Brixtonian said, the "which are" phrase isn't necessary, and removing it makes the sentence more succinct.

However, the second reason is that removing the connecting phrase removes a potential ambiguity in the meaning of the sentence. Specifically, it makes absolutely clear the order of events. That is, first, the humans send messages, and then they are picked up by the antenna. However, if the connecting phrase is left in, there is the possibility of a slight ambiguity, more easily seen if I add one more word:

Instead, my antenna picks up messages which are then sent by humans back in the United State.

That reverses the order: first the antenna picks up the messages (from goodness knows where), and only then are they sent by the humans (again, to who knows where).

Now I've added the word "then" to make the effect clear, but the effect is still there, albeit less obviously, even without the "then". There is still scope for the tiniest confusion in the mind of the reader, and removing the "which are" completely avoids that.

One other thing. You suggested that "which are" had been removed. But another option would be "that are". In theory, the ambiguity I mentioned could perhaps be avoided by choosing either "which" or "that", depending on what event order was intended. In theory. But in practice, the typical native speaker uses "which" and "that" interchangeably, and wouldn't know a restrictive clause from a non-restrictive one if either of them jumped up and bit him on the leg that was furthest west, which could be quite painful. So it's rarely possible to figure out precise intent from the choice of word, and so my explanation still stands.

  • 2
    I think you mean "relative clause", not "relative cause", in the first sentence
    – Stuart F
    Jun 27 at 16:32
  • 1
    Yup. Thanks for pointing it out, and to @JohnLawler for fixing it.
    – tkp
    Jun 27 at 23:08

The reduction of a relative clause (a clause normally starting with that or a wh-word, and modifying the noun before the clause) is frequently done by the rule known technically as Whiz-Deletion.

This rule applies only to relative clauses in which:

  1. the relative pronoun (i.e, that, which, who) is the subject of the relative clause
  2. the first auxiliary verb in the relative clause is a tensed form of be (i.e, is, are, was, were)

Condition (1) won't apply if the relative pronoun is the object of the clause, for instance, like

  • He knows the man [that you met yesterday],

where the relative pronoun that is the direct object of the clause -- you is its subject_.

Condition (2) applies often, since be is the auxiliary for the Progressive construction (is reading), the Passive construction (was already written), as well as all predicate adjectives (is funny) and predicate nouns (was a murderer). It's so common, in fact, that its appearance is often predictable, and therefore deletable.

The rule itself is simple: a subject relative pronoun and the form of be following are simply deleted, leaving only the verb phrase as a post-nominal modifier. If the remaining verb phrase consists of only one word, it can precede the noun it modifies. Thus there is no difference except length of expression between a man who is silly and a silly man.

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