GERUNDIVES
A gerundive is a verbal adjective - this is a verb form used as an adjective.
As it becomes an adjective, it must agree with its noun in number, gender and case - declines like 1st and 2nd declension adjectives e.g. bonus, -a, -um.
It is formed the same as the future passive participle - e.g. amandus, audiendus (see the participles section for more on declensions of participles).
The only use of the gerundive you need to learn is ‘ad’ + gerundive to show purpose!
This is ‘ad’ + noun and gerundive in the accusative case
E.g. miles e castris exiit ad hostes oppugnandos = The soldier left the camp to attack the enemy