Anicca is often translated as impermanence.
You may have seen it in a sequence that roughly goes like this:
Q1: Is form permanent or impermanent?
A1: Impermanent.
Q2: What is impermanent is that suffering or happiness?
A2: Suffering.
Q3: Is of that sound to say 'this is me, this I am, this is myself'?
A3: It isn't.
A3 might be clear if it is understood that if form were you, yours, yourself, it would be possible to have your form however you would like; it would certainly not be a liability to suffering. And for Q1 you might find a reason to give the same answer as given in A1. However... A2 then is not evident at all, which means an opposite answer could then be a valid too and clearly that is not the intent here. This must have something to do then with the translation of anicca. So, let's look into this.
Let's start by making two groups. Group A for impermanence and kindred words, and group B for some other options.
Now for group A. Many people already know that form is not permanent. And what is their answer to this? 'Live life to its fullest! Enjoy while it lasts!' The negatives and the positives are seen as inevitable parts of life and one can only try to get as much of the positives as one can. And if they take this statement of things being impermanent to heart they would be able to accept that there is no magical potion to make them everlasting, nor such a favour to expect from a god, or from scientists finding a scientific solution. They won't have to worry about those things to exist and thus can they focus with an even lesser reserve to live their life to its fullest. So the effect this impermanence has is not one that makes people want to turn away. Thus is the answer to the second question not evident at all, which means that the sequence has become invalid.
Then for group B, let me explain it like this: Suppose you have in another country a family vacation home where you and your family are staying. And since working on the building is part of your family's fun the house is entirely made out of untreated wood. So if someone comes along to tell you that it is impermanent you can agree to it, even if you don't know what the remark was exactly about. Was it that the house won't survive for generations? or woodworms? or was it that you can't stay there long-term? It is after all not a permanent residence. In any case you can agree to it so you gave it a thumbs up. But suppose this person was an official and your reaction was not what he expected. Figuring his English wasn't good enough he signs his colleague to help him out. And you learn that apparently, because of old minings and the recent earthquakes, the area has become very unstable and an evacuation alert was given. Would you now enjoy your stay like there is no tomorrow or would you take your loved ones and evacuate? Why? Because the liability to suffering is evident. It doesn't matter to much if the experience is an enjoyable one or not, preferable it is, but safety first! Unstable is found for anicca in the dictionary, and now 'sufferingly', as answer to the question now translated as 'Is what is unstable sufferingly or happily?' is evident.
Perhaps it might seem that the question 'Is form stable or unstable?' has a similar problem; why not answer it like 'Sometimes stable, sometimes unstable'? If so, what do you think, would it be better to validate something as stable at face value or after investigation? So then, what makes it that f.i. a house is unstable? What you'll arrive at is its support. And thus we need to look at the stableness of that support. Anything that is supported by something which isn't stable, is not stable either. Now form is inclined. And what are the characteristics of the inclined? There is the arising, passing and the alteration when stood. And as these characteristics are also inclined, they too arise ... etc. Looking at it this way we can see why this situation must collapse; the whole structure is unstable.
So the difference between these groups is not that innocent; group A is about existence through time, about views connect with eternalism and nihilism thus temporal (kālika) while group B is about what is atemporal (akālika), structural. The now valid sequence can be read as follows:
'What is unstable that is sufferingly, what is sufferingly that is not self and is thus not to be regarded as 'this is me, this I am, this is my self'.'
Pāḷi-English
Anicca (adj.) unstable.