Plato, Meno 76a

τί δʼ; ἐπίπεδον καλεῖς τι, καὶ ἕτερον αὖ στερεόν, οἷον ταῦτα τὰ ἐν ταῖς γεωμετρίαις; ἔγωγε καλῶ. ἤδη τοίνυν ἂν μάθοις μου ἐκ τούτων σχῆμα ὃ λέγω. κατὰ γὰρ παντὸς σχήματος τοῦτο λέγω, εἰς ὃ τὸ στερεὸν περαίνει, τοῦτʼ εἶναι σχῆμα· ὅπερ ἂν συλλαβὼν εἴποιμι στερεοῦ πέρας σχῆμα εἶναι. τὸ δὲ χρῶμα τί λέγεις, ὦ Σώκρατες; ὑβριστής γʼ εἶ, ὦ Μένων· ἀνδρὶ πρεσβύτῃ πράγματα προστάττεις ἀποκρίνεσθαι, αὐτὸς δὲ οὐκ ἐθέλεις

Well then, you speak of a surface, and also of a solid—the terms employed in geometrical problems? I do. So now you are able to comprehend from all this what I mean by figure. In every instance of figure I call that figure in which the solid ends; and I may put that more succinctly by saying that figure is limit of solid. And what do you say of color, Socrates? How overbearing of you, Meno, to press an old man with demands for answers, when you will not trouble yourself