I was curious, after asked this question by a student, to know what part of speech you would consider the word "my" in this sentence as:

My book is that one.

I browsed various dictionaries to see what part of speech they considered the word as. While some dictionaries like American Heritage and Merriam Webster consider it as an adjective, most others like Lexico, Cambridge, Collins, etc consider it as a determiner. When I searched for the distinction between both the parts of speech, I came across this webpage which says that the first difference is that while an adjective can be used predicatively, a determiner can only be used after a noun or noun phrase. So considering this distinctive quality, in the above written sentence it seems to me that "my" is definitely a determiner there, but I still don't have courage to say a prestigious dictionary like M-W can be wrong. I would appreciate any help in the matter.

  • 1
    (1) There is no reason it can't be both things. (2) Different people define (or consider) terminology differently. In this case, it depends on who you ask. May 25, 2020 at 15:40

2 Answers 2


One example certainly isn't enough, but this one example here might be very helpful. 

In the sentence above, there are two instances of the spelling "one".  The first acts as a determiner.  The second doesn't, since that role is filled by the word "this". 

One way to look at this is to say that there are several different words "one".  From this perspective, one could imagine a set of homonyms, each differing from the others perhaps only in word class: including the determiner "one", the plain adjective "one", the pronoun "one", and the common noun "one". 

That perspective exists, but personally I don't like it.  It lacks parsimony.  It adds a complication that seems to lead more often to confusion than clarity. 

I prefer to describe "one" as a pair of homonyms, an adjective and a noun.  From my perspective, the adjective "one" can act as a determiner or as a substantive, meaning I need only one part of speech to explain the plain-adjective-like, determiner-like and pronoun-like behaviors of this one word. 

My book is that one. 

Here, I describe "my" as a personal pronoun, specifically the singular first-person attributive genitive pronoun. 

Oddly enough, personal pronoun doesn't appear among the options you've considered. 

Even the page you cite notes that "some grammarians consider determiners to be a part of adjectives."  Merriam-Webster grammarians are apparently among them.  There is no real conflict between Webster calling it an adjective and Collins calling it a determiner.

From my perspective, determiner is a semantic role, not a grammatical word class.  It's a role predominantly filled by adjectives, and sometimes filled by genitives.  From my perspective, there is no conflict between this "my" being both a determiner and a pronoun. 

How someone with a different perspective might otherwise resolve the apparent conflict is not something that I can explain. 

  • Don't you think "my" should be a possessive pronoun considering that it's a possessive case of the personal pronoun "I"? I'd be glad to know what's your say.
    – kelvin
    May 26, 2020 at 7:25
  • That's just another example of different people using different labels for the same thing. You say "possessive case", and I say "genitive case". We're still pointing at the same set of word forms: my and mine, your and yours, her and hers, and so on. May 26, 2020 at 13:32

There's a discussion of this here:
Stack Exchange ELU "is a determiner...?"

The consensus seems to be that they are separate parts of speech, not interchangeable with each other, that work differently.

Another reference that agrees:
Quora.com "are determiners adjectives"

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