The most precise definition of Brahman in any Upanishad. Three terms — not three attributes added to a substrate, but three intrinsic indicators that each exclude a different inadequate way of understanding what Brahman is.
Three words. Each one does a specific job. Together they point at what Brahman is — and just as precisely, what it is not.
The three terms work together: Brahman is what remains when unreality, insentience, and limitation are all set aside. What that points at is the pure consciousness that has no edge, has always been, and needs nothing to illuminate it.
Śaṅkara's commentary distinguishes two types of indicator (lakṣaṇa): a taṭastha-lakṣaṇa identifies something by reference to something else (like pointing to a house by saying "the one next to the tree" — the tree is not part of the house, just a pointer). A svarūpa-lakṣaṇa describes the thing's own intrinsic nature.
Śaṅkara argues that satyam jñānam anantam are svarūpa-lakṣaṇas — they describe Brahman's own nature, not external pointers to it. But crucially, they are not three separate attributes added to a substrate. Brahman is not a substance that happens to be real, conscious, and infinite in the way a person can be tall, clever, and kind. The three terms are three angles on one non-composite reality: being-consciousness-infinitude, inseparably and without parts.
Why is jñānam (consciousness) included as a svarūpa-lakṣaṇa rather than being implied by satyam? Because sat (being) alone would not distinguish Brahman from the being of insentient matter. A rock exists — but it does not know. Brahman's being is conscious being. The inclusion of jñānam as a separate term ensures the definition points at awareness rather than mere existence.
Similarly, anantam is not redundant with satyam. Something could be real but finite — like a rock again, which is real and has clear limits. The three terms together exclude every inadequate conception: the dream-like (excluded by satyam), the insentient (excluded by jñānam), and the limited (excluded by anantam).
The relationship between the Taittirīya formulation and the more common Sat-Cit-Ānanda triad is worth examining carefully. Satyam ≈ Sat (being), Jñānam ≈ Cit (consciousness). But Anantam (infinite/limitless) does not map straightforwardly onto Ānanda (bliss). The difference is significant: anantam is a logical property (no limits), while ānanda is an experiential quality (the bliss of having no limits). The Taittirīya formulation is more strictly philosophical; Sat-Cit-Ānanda includes the experiential resonance of liberation.
Śaṅkara himself uses both formulations. In the Taittirīya Bhāṣya he unpacks anantam in terms of three types of limitation (pariccheda): spatial (Brahman is not bounded by any region), temporal (Brahman has no beginning or end), and objective (Brahman is not an object among other objects — there is nothing that is not Brahman). All three are excluded by anantam.
The three limitations Śaṅkara identifies are also the three ways avidyā operates: we experience Brahman as limited by space (this particular body, this particular location), by time (this particular lifetime, this particular moment), and by objecthood (this particular entity among other entities). The recognition of Brahman dissolves all three: the self is not located, not temporally bounded, and not one thing among others.