Formal
Hegel (Logic of Essence, opposite of real)
Formal designates abstract, content-empty form. Formal possibility is mere freedom from contradiction (thinkable, but without real conditions). Formal law is external rule without inner necessity. Formal identity is empty tautology (A=A). The reproach "merely formal" means for Hegel: without concrete content, external. Formal logic (Aristotle) deals with forms of thought without content. Hegel's logic wants to be full of content --- to unite form and content.
Origin
Lat. formalis (concerning form). Scholasticism: formal vs. material principles. Kant: formal logic vs. transcendental logic. Hegel criticizes abstract formality, demands concrete form.
In Hegel
Enc. §143 (Possibility); §121 (Ground)