Sorry. I had been busy and did not upekkha100’s latest comment.
Tilakkhana (ti + lakkhana) are three major CHARACTERISTICS or properties of the real nature of this world. There are several other characteristics too: asubha (not beneficial), rogato (subject to disease), etc.
These characteristics are understood gradually when one starts on the Path. Significant improvements (or jumps) in understanding happens at the stages of magga phala.
– For example, at the Anagami stage one realizes Tilakkhana to a more deeper level where one’s mind has realized that engaging in activities for sense pleasures is meaningless.
– However, one cannot get there without understanding Tilakkhana at a lower level at the Sotapanna stage.
This is what was discussed in the recent post: “Is It Necessary for a Buddhist to Eliminate Sensual Desires?”
Another point is that there are many ways to describe each of anicca, dukkha, anatta characteristics. For a given person, one aspect of anatta may be easily understood than another aspect.
– For example, “atta” can mean a state that is “unchanging (no death), no unexpected change (no viparinama), and is the ultimate happiness”. What the Buddha is said such a state DOES NOT EXIST in this world. Thus as long as one is bound to this world of 31 realms, one BECOMES “anatta” (helpless or subject to suffering).
– Nibbana is THAT STATE and one needs to overcome the sansaric bonds to this world (ten samyojana) in order to get there. That is real “atta” state and one who gets there becomes a true “attā”.
This post discusses that aspect: “Anatta – the Opposite of Which Atta?“.
Akvan summarized what I said above: “2) When it is said that anatta becomes completely true for an arahanth, I think it means that only when a person reaches the arahanth stage does one fully comprehend anatta.”