I encountered this in Ch. 7. Unless I missed it in previous chapters, I don't think this concept was discussed prior to this.
It kind of alarms me that I was unaware of this and was wondering how I would know which nouns use the genetive as nouns such as cura do.
I'm not sure what part of grammar you're on about here - I don't have wheelock.
The genitive of characteristic is generally found in sentences like:
hominis est errare
It is the characteristic of a human to err/It is (the mark) of men to err
Est imperatoris superare hostes
It is the characteristic of an emperor to overcome enemies/It is the duty of an emperor to overcome enemies
I think I mentioned in another thread that the genitive was one of the more widely used of latin cases. I incorrectly gave the name of this use as the genitive of characteristic. For instance, anger at his retreat would be translated as ira fugae
. Generally when you want to connect one noun to another, you wouldn't use a preposition but the genitive case. The noun phrase "Care for my mother" would be translated as cura matris
. This is called the objective genitive - if cura were a verb, mater would be its object. There is also the subjective genitive. amor matris
can mean the love by/of a mother. If love were a verb, mater would be it's subject. These two can be confused of course. odio generis humani
can mean (i) on account of (ablative of cause) their hatred of the human race or (ii) on account of the hatred the human race held for them. If you're a student of Tacitus, wondering why christians were burned for the fire in Rome, you would do well - and better than most scholars - if you could tell these uses apart. They do after all mean the exact opposite!
The genitive can be used for internal characteristics, qualities or desciptions. This is also sometimes called the genitive of characteristic, but a better name would be the genitive of quality.
formica magni laboris
(ant of much labor/much-toiling ant)
vir magni ingenii
(man of much ability)
The grammar books say that the genitive should be used for internal characteristics, and the ablative for outside/external traits:
Est candido capite
(he is with a bald head/he's bald)