(a) Determiners are words that are used before nouns to provide more information about the noun, such as quantity, possession, or definiteness. Examples of determiners include articles (a, an, the), demonstratives (this, that, these, those), possessives (my, your, his, her, its, our, their), quantifiers (some, many, few), and numbers (one, two, three).
(b) Modern grammarians regard determiners as an independent part of speech in the English language because they play a crucial role in determining the meaning and function of a noun phrase. Determiners help to specify whether a noun is definite or indefinite, singular or plural, and whether it is possessed by someone or something. Without determiners, it would be difficult to convey precise meaning in a sentence.
Furthermore, determiners can also function as pronouns, replacing a noun in a sentence. For example, in the sentence "This is my book," the determiner "this" acts as a pronoun replacing the noun "book." This versatility and importance in sentence structure support the argument that determiners should be considered an independent part of speech in English.