SuttaCentral – Sujato renders it ‘principles’, Nyanamoli Thera leaves it untranslated, I.B. Horner has ‘mental objects’, and Suddhāso Bhikkhu has ‘phenomena’
For example it list the hindrances - How, monks, does a monk live contemplating mental objects in the mental objects of the five hindrances?
Herein, monks, when sense-desire is present, a monk knows, “There is sense-desire in me,” or when sense-desire is not present, he knows, "There is no sense-desire in me.
or the ayatana
How, monks, does a monk live contemplating mental objects in the mental objects of the six internal and the six external sense-bases?
Herein, monks, a monk knows the eye and visual forms and the fetter that arises dependent on both (the eye and forms);[24] he knows how the arising of the non-arisen fetter comes to be; he knows how the abandoning of the arisen fetter comes to be; and he knows how the non-arising in the future of the abandoned fetter comes to be.
He knows the ear and sounds… the nose and smells… the tongue and flavors… the body and tactual objects… the mind and mental objects, and the fetter that arises dependent on both;
The word dhamma has a number of meanings according to the context in which it is used. It can mean: natural phenomena, mental objects, a state, truth, reality, wisdom, actions, good actions, practice, cause and offence. Also, in English usage Dhamma (there are no capital letters in the Pāļi language) can mean the Teachings of the Buddha or the texts which contains those teachings.
Here, in this context dhamma is any natural phenomenon that is not a concept and it is specifically referring to the five hindrances, the five aggregates of clinging, the six internal and external sense bases, the seven factors of enlightenment and the Four Noble Truths.