According to the book, grammatical terms, e.g., subject, object, noun, verb, adjective, etc. should not be defined by meaning, but by grammatical properties.
For example, an adjective has combinations of the following properties:
(1) functions as attributive modifier or predicative complement
(2) can inflect for grade, e.g., better, harder; or form comparative and superlative adjective phrases, e.g., more interesting
(3) can be modified by adverb like "very," or "too"
One thing I notice is that sometimes adjectives are easily identified with these properties because of the context.
For example, the word "hard" in "he is a very hard worker" is obviously an adjective because it is modified by "very" and it functions as an attributive modifier (or, more specifically, heads an adjective phrase that functions as an attributive modifier).
But sometimes adjectives are not easy to identify because the context barely provides anything for you.
For example, in the sentence "The rock is hard" the word "rock" has the only property of an adjective - functioning as predicative complement.
In the book, the authors manipulate the sentence like this to 'test' whether "hard" has any other properties of adjectives. They might add "very" to the sentence to see whether or not "hard" can be modified by "very.
However, sometimes I think they go too far.. Like, in this example from the answer key to the book, the authors try to 'test' whether "barking" can form a comparative phrase by putting it in a completely new sentence (as highlighted).
- Which of the underlined words below are adjectives, which are verbs, and which are ambiguous between the two categories in the examples given? Give evidence for your answers.
Example: The dog is barking again.
Answer: *Barking is a verb. It has a corresponding preterite form (The dog barked again), but doesn't have a comparative (*Rex is more barking than Fido). It doesn't accept such modifiers as very (*The dog is very barking). It can't occur in predicative complement function: be in the example is the progressive auxiliary, and can't be replaced by such verbs as become and seem (*The dog seems barking).
So my question is: Are there restrictions on how you can 'test' for grammatical properties? Can I just put the word in question in any sentence to see if it has any other properties?