The following is based on my understanding, of the dhamma and also languages. So please point out any mistakes.
The pali in this section is as follows. Aniccatoti, aniccā¬nu¬passanā. Which I take to mean, seeing it as aniccha is contemplation of aniccha. So each pali word is linked to the contemplation of aniccha, dukka and anatta.
Siebe said: In the above you see that all kinds of synonyms have been used to explain impermanence.
I don’t think these words can simply be taken as synonyms but regarded as different ways of seeing / understanding / contemplating aniccha. So, seeing things as perishable, subject to change etc. are different ways of understanding aniccha. But aniccha does not simply mean that it is perishable or subject to change. If perishable simply meant aniccha then the following don’t make any sense Aniccatoti, aniccā¬nu¬passanā. Dukkhatoti, duk¬khā¬nu¬passanā. Anattatoti, anattā¬nu¬passanā.
Under anattanupassana, the contemplation of anatta, the following are given; Rittatoti, Tucchatoti, Suññatoti, and Anattatoti, anattā¬nu¬passanā. These have been translated as empty, void, having no core and not-self respectively (I believe that Sunnatoti has been mistakenly placed under dukka, when it should be under anatta).
Here I don’t agree with the translation of Tuccha as void. I understand tuccha to mean something lowly and something to be disgraced of. Also I would say that a better way of explaining sunna would be to say having no value / substance. Sunna (Shunya) means empty and if we say something is empty the emptiness is always relative. For example if we say a glass is empty, what we actually mean is that the glass is empty of milk. But there can be air in it, but for our intents and purposes it is empty. So even here sunna (empty) does not mean that it is absolutely empty but that it is empty of any value or substance.
Asārakatoti, anattā¬nu¬passanā is also mentioned but I did not see it in Siebe’s list. I take asaraka to mean having no value to take / having nothing good to extract.
Of course, each one of us will understand aniccha, dukka and anatta in different ways, based on our backgrounds and ways of looking at things. Therefore, it is important that we don’t just stick to one single word (impermanence and non-self) to understand aniccha and anatta. Like Lal has mentioned these words are packed with meaning and it is hard to explain it using a single synonym. I would go on to say that aniccha, dukka and anatta is actually an understanding rather than just a simple word.