Comparative words after the subject

Question

I'm really having trouble figuring out how to describe a clause describing a subject which contains a comparative adjective (or an adjective of equality). For example:

Children [shorter than four feet] are not allowed on the ride.

Words [larger than eight letters] confuse me.

The number [equal to 6] is the correct answer.

Which word [synonymous with "sad"] is also a color?

Is this a relative clause without a relative pronoun? Also, would these clauses be considered non-restrictive, therefore requiring commas?

Answer 1

As far as my knowledge and internet research goes these are all (or should be, depending on what meaning you are trying to convey) restrictive relative clauses with a zero-pronoun.

Children [that are] shorter than four feet are not allowed on the ride.

Words [that are] larger than eight letters confuse me.

The number [that is] equal to 6 is the correct answer.

Which word [that is] synonymous with "sad" is also a color?

The words in brackets are what is left out by the zero-realisation.

If you use the relative clause to add some information that does not change the meaning of the modified noun then you would have a non-restrictive relative clause and would have to use commas.

Words, larger than eight letters, confuse me.

This would then result in the meaning of the sentence changing to words confuse you (because non-restrictive relative clauses add information that can be omitted, generally speaking) although this would be a weird example of a non-restrictive relative clause.

I hope this helps somewhat.