There are several synonyms for the phrase "grammatical theory" that can be used to describe theories and principles related to language and grammar. Some options include linguistic theory, syntax theory, grammar theory, and language theory. Each of these terms encompasses a broad field of study that explores the ways in which language is structured and how it is used in communication. These theories and principles are essential for understanding how language works, from the tiniest details of syntax and word choice to the larger concepts of meaning and intention. By studying grammatical theory, linguists and other language professionals can gain a deeper understanding of the complexities of human language and how it shapes our communication and understanding of the world around us.