In the Spanish language, the relative sentences can be specific or determinative and explanatory or incidental. The first ones determine the antecedent, specifying it; the latter do nothing but express a circumstance of it. Explanations and examples
If I say:
Juan, who is diligent, works tirelessly
The sentence "that is diligent" does not determine or specify the noun Juan, but indicates a characteristic and characteristic quality of it, and therefore it is explanatory.
In explanatory sentences the relative sentence is separated from the antecedent by a slight pause in the recitation and by a comma in the writing. In these, the relative that can be replaced by the pronoun that preceded the article, according to the gender and number of the antecedent; but in the specifications can not always make such a substitution.
It can be said:
Pedro and Juan, who are friends (or who are friends), helped each other
A condition that distinguishes the relative ones from the incidental or explanatory ones is that they can be suppressed without ceasing to be true the meaning of the main sentence; but those, no. It can be said:
Juan works tirelessly
the relative sentence
The pause that in the incidental sentences is made between the antecedent and the relative, and the comma with which it is indicated in the writing, are so necessary, that only by them the class of these sentences is distinguished in many cases. If I write:
the allies who did not want to submit were put to the knife
the relative sentence is specific, and states that not all the allies, but only a part of them (those who did not want to submit) were put to the knife; but if I write
the allies, who did not want to submit, were put to the knife
indicated that they were all without exception.
Explanatory or incidental ones can become independent sentences or adverbial subordinates, substituting the relative pronoun for a conjunction; like this:
the allies, because they did not want to submit, were put to the knife
o well
the allies did not want to submit, and were put to the knife
but you can not do the same in all the cases we have seen, they are small. You can not say all the cases, because we have seen them, they are small.
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