If I say "today was good day," and add an a in the right spot like, "today was a good day," from a broad view, is what I just did considered a grammatical change or something else?
closed as not a real question by user2683, FumbleFingers, Mitch, kiamlaluno, JSBձոգչ Dec 6 '11 at 15:23
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Yes, although change is perhaps not the word you want. In the second sentence, with a, the phrase a good day is a Predicate Noun Phrase -- i.e, although the official verb is was, the meaningful predication part is a good day. Nothing has been changed here; the first sentence doesn't exist as a source. But there is a distinction to be made, and it depends on what kind of predicate the sentence has.
Verbs are the prototype predicates, and English requires a tensed verb in every finite clause to be marked for tense; but there are other kinds of predicates, like Predicate Adjectives:
- She is tired.
- He is very tall.
which require some form of be.
Predicate NPs (Predicate Nouns for short) also require some form of be, but in addition they are marked by an indefinite article, a. That's why your first sentence is wrong: it's ungrammatical to use a predicate noun without a, just as it would be to use it without be. But it's equally ungrammatical to use a with a predicate adjective.
- *Today very hot.
- *Today a very hot.
- Today was very hot.
- *Today was a very hot.
- *Today good day.
- *Today a good day.
- *Today was good day.
- Today was a good day.
Yes, it's a grammatical change. It's not a spelling change, a punctuation change, or a vocabulary change.