Why are there so many definitions of Tathata and how does one know when to use each one when reading a text?
tathata = dependent origination
tathata = dharmata
tathata = see the truth of all things, to see the reality of the things. The wisdom arising to the person who practises insight meditation.
"Awakening of Faith in the Mahayana" describes the concept: "In its very origin suchness is of itself endowed with sublime attributes. It manifests the highest wisdom which shines throughout the world, it has true knowledge and a mind resting simply in its own being. It is eternal, blissful, its own self-being and the purest simplicity; it is invigorating, immutable, free... Because it possesses all these attributes and is deprived of nothing, it is designated both as the Womb of Tathagata and the Dharma Body of Tathagata."


Tathagata is tathata + gata, or gone to tathata.