Humanus is always adjective in latin, so I believe that there must be a noun in genitive case masculine or neutre after this word, something like de humani corporis scientia (the science about human body), de humani moris colloquio (the conversation about human costumes). So the answer is of human adjective

Very helpful, thank you!

I) "De" introduces the argument and wants the ablative case, on the other hand "humani" can be only a (masculine) plural nominative or a (masculine or neuter) singular genitive. This is the reason because Ivana has understood that there had to be another word (fabrica), in the ablative case, introduced by "de" and related to the singular genitive (here, plural nominative makes no sense). So the translation is "About (de) the Structure (fabrica - ablative) of Human Body (humani corporis - genitive)", If you want to speak "about the human body" or "about the human being", you must say respectively "de corpore humano" or "de homine". Also "de re humana" for "about the human things", "about the humanity". --- II) The differentiation between "V" and "U" started in 1524 and went in common use at the end of XVII century. Till then, the characters "V" and "u" represented both the sounds, the consonant "V" (which, on the other hand, in Classical Latin was pronunced as a "w") and the vowel "U". The "De humani corporis fabrica" was published in 1543, before this differentiation.

Great, I was hoping it would function as an adjective. De humani corporis scientia/fabrica is actually the cause for my asking. The illustrations are just wonderful but in understanding the human body, I understand it to be imperfect and vulnerable, i.e., the other sense of the word human. Is de humani correct or should it be de humanus for what I'm trying to express? Another question: one of the typefaces used in the book has the letter U looking like a V, e.g., DE HVMANI. Why is that? Was it just standard of that time? I know that many brands, now, are doing the same in their word logos in attempt to be creative.