Question: What is the grammatical or syntax term for a *sentence structure* in which there are more than one subject or more than one object continuously in the sentence? 

Example 1: 
In this sentence, the there are three [**object**](https://dictionary.cambridge.org/grammar/british-grammar/about-words-clauses-and-sentences/objects)s. 

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> He studies **English, Spanish** and **Portuguese**.
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Example 2: 

In this example there are two subjects: 

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> **The boy and the girl** ate the food.
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Answer: 
Not sure about how it is called in grammar of English, but "English, Spanish and Portuguese" is just the direct object, and "the boy and the girl" is just the subject. Each structure can be formed by more than one word and by more than one real world item.
It is called: **conjunction-reduction**.

In transformational grammar it is a rule that reduces coordinate sentences, applied, for example, to convert "*John **lives** in Ireland and Brian lives* in Ireland" into "*John and Brian **live** in Ireland*". ([Collins](https://www.collinsdictionary.com/dictionary/english/conjunction-reduction))

Credit: @jlawler in the comment.