The two main and different defintions of the word dhamma are, one, the teachings, and in this context, it is (simply) translated as ‘phenomena’. It’s not Abhidhammic, but repeatidly present in the EBT.
See:
sabbe sankhārā aniccā
All formations (conditioned) are impermanentsabbe sankhārā dukkhā
All formations (conditioned) are sufferingsabbe dhammā anattā
All phenomena (unconditioned—i.e., including Nibbāna—and conditioned things) are not-selfNibbāna is not included in the first two, for the reasons that you described [Nibbāna is not conditioned (i.e., a formation) and by definition cannot be dukkhā], but it is a dhamma (it is phenomena) and therefore is classified in the third characteristic (all things are not-self).
![](https://discourse.suttacentral.net/user_avatar/discourse.suttacentral.net/martin/48/26575_2.png)
Not me, but my point stands. Having followed this discussion I still think the suttas are ambiguous on the question of whether Nibbana is a transcendent reality, or a state of mind, or something else.
Nibbāna is unconditioned. It is categorically and solely a result (for the lack of a better word) based on the absence of the defilements/fetters (kilesa/saṃyojana) and dukkha—nothing more, nothing less.
You have the common assumption that Nibbāna is a magically blissful state. Nibbāna is probably highly blissful due the complete/absolute absence of dukkha; but not blissful in the way “nirvana” is described by the mainstream.