Definite article still confuse me even after having got a lot of help on the site. What I noticed is that we use "the" when we talk about something particular or something unique. But what with this sentence:
1) This is a thing not to worry about.
I think if I said 2) "This is the thing not to worry about", it would mean that this is the only thing not to worry about, but what if I mean it's just one of them - should I use indefinite article then? But than it seems a strange structure to me...
Saying "this is a thing not to worry about" sound like "this is a case not to worry about" - never met such a thing. Never heard "that's a case either"...
1) Is the sentence 1 correct?
2) Can the sentence 2 mean that it's one of the things not to worry about?
3) If the answer for the 2nd question is "yes", can I say: "I am lazy. This is the thing not to worry about. I am angry too. This is also the thing not to worry about." Or "a" should be used?
I know I asked similar questions, but still in a muddle and want to clarify this all... Thank you in advance!)