You mention at one point だ is the informal form of です. On the other hand, there’s Tae Kim who vehemently denies this In his excellent guide to J. grammar he gives a clear explanation. Now, although I agree with Tae Kim, at the same time I would say that in some cases a sentence which one would want to make formal is made by simply replacing だ with です, even if it’s in the past/negative/negative past. This makes it kind of hard for me (and I think I’m not the only one to know how to exactly feel about だ and です, especially since it’s an important part of everyday spoken Japanese. I know I can do the whole “go with the flow” approach (and I probably will that this and this sentence means that and that, I think it would be cool if you could offer your view on the matter.

So, what’s the truth about だ and です? Is it that they are grammatically different words which sometimes simply take the same meaning (apart from the difference in politeness)?

Thanks a lot in advance!

An older student, with diminishing eyesight, I am much encouraged by this simple decision which has materially supported my progress. My son has loaned the book copy of Heisig to a friend and with this large size to study, I find I can move forward with some confidence in the stroke order.

In the explanation: だから 早く 起きて!

In the comic, it is written: だから早くおきろ!