That's great, Reenie. Modern linguistics, of which Noam Chomsky is said to be the father, was already well under way while you were in grammar school. However, its findings and approaches doubtless were not part of your grammatical catechism.quote:I learned my grammar in Catholic schools in the 60s and 70s, which I guess is before the dawn of modern linguistics!
Did you by chance study the Reed-Kellogg sentence diagramming method in Catholic grammar school? I suspect that that is the source of your difficulty. That approach to diagramming was developed in the mid-1800s, long before the dawn of modern linguistics.
In Reed-Kellogg sentence diagrams, which were for teaching youngsters grammar, determiners branch off of the lines on which nouns are drawn in the same way that adjectives do. If that is how you're thinking about things, your misconceptions are totally understandable.
No, determiners do not function as adjectives. In the phrase "this book," "this" is not an adjective; it is a determiner. In the phrase "my book," "my" is not an adjective; it is a determiner. Again, though, your Reed-Kellogg diagrams won't show you the difference.quote:Based on what you have said, it seems that demonstratives can function as adjective or determiner (this book/ i want this). Possessive pronouns only functionas adjectives (my book).