Today in English lesson, the teacher wrote this example on the board:
"I wish I hadn't left a valuable things in a car."
I told him we shouldn't use 'a' before a plural noun but he didn't listen and claimed that the sentence is correct....I still can't understand why, and I even think it should be 'the car', not 'a car'.
Unfortunately, that example sentence is ungrammatical. You can't use a plural noun with the indefinite article "a", because it's always singular. Either the definite article ("the") or the zero article (nothing at all) could be used in place of the first "a" in the sentence.
For the second one, "a" isn't really wrong, since the point is not so much a particular car as just the fact of a car in general. But it's probably not ideal, since some particular car would naturally have been involved. So "the" is somewhat better in this case as well.
That leaves us with four valid sentences:
"I wish I hadn't left valuable things in a car."
This doesn't necessarily refer to any specific event, although it's unlikely that this happened more than once. The speaker regrets having ever done this.
"I wish I hadn't left the valuable things in a car."
This refers to some specific set of things that was left, based on the context (either before or after).
"I wish I hadn't left valuable things in the car."
The speaker is particularly thinking about the specific car, and regretting the valuables in a more general way. Perhaps they attracted the wrong sort of attention to the car, and thieves stole the car or broke its windows.
"I wish I hadn't left the valuable things in the car."
This focuses on a particular event and the details of that. The car is an important background detail.
The differences here are fairly subtle, but they do suggest interesting distinctions in the speaker's thoughts.
One exception that comes to mind that doesn't seem to be listed elsewhere is in the example "Thank you for a fantastic 25 years". This is grammatically correct for the following reasons:
Idiomatic Expression: The phrase "a fantastic [number] years" is idiomatic and commonly used to refer to a specific period of time, regardless of whether the noun following "a" is plural. It's a set phrase that doesn't strictly adhere to the singular/plural rule usually associated with articles like "a" or "an."
Singular Sense of the Phrase: The phrase "a fantastic 25 years" is understood to refer to the entirety of the 25-year period as a singular concept or unit of time. It doesn't necessarily imply that each individual year is fantastic but rather the overall experience or duration.
Accepted Usage: English allows for flexibility in expressions and idiomatic usage. Similar constructions can be found in phrases like "a great five days," "a wonderful two weeks," etc., where a singular article precedes a plural noun denoting a specific duration or period of time.
