 The first two requirements appear in many texts, but the third emerges most clearly in the  Euthyphro.  The Euthyphro seems to require that a definition state the essence (ousia) of the thing being defined, by contrast with a statement of that thing’s non-essential attributes (pathe). A statement of non-essential attributes could be true without qualifying as a definition. The statement “reverence is what all the gods love” states only a pathos, because it does not explain what makes something reverent. We are left to speculate about what would count as stating the essence of reverence; probably it would state what makes things reverent in the way that having three straight sides and three angles makes a plane figure a triangle, whereas giving delight to geometers does not. Clarification for the explanation requirement comes from a further requirement, that the explanatory cause of Xness must be always X (the synonymy requirement). Hence Socrates rejects answers to “What is the fine?” that identify entities that are not reliably fine (e.g. Hippias Major 289b;cf. Phaedo 105d).