5,What is the history of phraseological units?

39,What is syntax theory?
Syntax theory is the study of the rules and principles that govern how words and phrases are combined to form sentences in a language. It is a branch of linguistics that focuses on the structure, ordering, and relationship of words and phrases in a sentence, as well as on how the meaning of a sentence is derived from its structure. Syntax theory aims to describe the underlying structure of language and to develop a set of rules that can be used to generate and analyze sentences in a language. These rules involve principles such as constituent structure, phrase structure, and grammatical relations between words and phrases. One of the main goals of syntax theory is to explain how native speakers of a language are able to produce and understand an infinite variety of sentences, even those they have never heard before. It also studies the variation in syntax across different languages and dialects, and investigates the ways in which syntax reflects and shapes social and cultural norms.