How would you translate "they wave (in order) to greet him"? I can't find the right word for 'wave' (did the Romans even wave as a greeting?) and I've also forgotten how to use gerundives
I assumed waving was a universal sort of human greeting, but there doesn't seem to be a Latin word for it? Manus agitant ut eum salveant (they wave their hands in order to greet him) should get the idea across, though.
The gerundive is a future passive participle formed from the root of the infinitive. For coquere, you get coquendus -a, -um (declined like a regular first/second declension adjective).
Like any adjective, it's used either to modify a noun or on its own as a substantive, and like other Latin participles, takes over a lot of constructions that in English would be represented by a separate clause. So instead of saying "he brings the food that will be cooked", you can say cibum coquendum fert: he brings the to-be-cooked food.
There is often a sense of necessity or purpose: not just that the food will be cooked, but that it must or ought to be. This allows it to stand in for the gerund sometimes, as in eos liberandos volunt instead of eorum liberandum volunt.
