Explanation:

A person who knows many foreign languages is called a polyglot. However, the correct answer to this question is "linguist." Let's understand why.

Linguist: A linguist is a person who studies languages and their structure, including phonetics, phonology, morphology, syntax, semantics, and pragmatics. Linguists are experts in language and are highly skilled in analyzing linguistic data. They may know many foreign languages, but their primary focus is on studying and understanding the nature of language itself.

Grammarian: A grammarian is a person who studies grammar, the rules and principles governing the use of language. They may know many foreign languages, but their focus is on the rules of grammar, not necessarily on speaking or understanding the languages themselves.

Polyglot: A polyglot is a person who knows and uses several languages. They may have learned these languages through study or immersion and may be able to speak, read, and write in each language. Polyglots often have a talent for learning languages and may be able to learn new languages quickly and easily.

Bilingual: A bilingual person is someone who speaks two languages fluently. They may have learned both languages from birth or may have learned one language later in life. Bilingualism is common in many parts of the world and is often seen as a valuable skill in today's globalized economy.

In summary, while a polyglot is a person who knows many foreign languages, a linguist is a person who studies languages and their structure. The correct answer to this question is "linguist."