What is the gerundival attraction?

Although the name sounds scary, it is easier that it seems. In Latin when a gerund has an object, there is a tendency to harmonise the terminations of the two, so the object will agree with the sense of the object. To understand this better we should look at some examples. In the construction ‘libros legendo’ (by reading books), the gerund is in the dative case, so ‘libros’ will ‘be attracted’ in the same case and ‘legendo’ will agree in number and gender with it. So, this construction becomes ‘libris legendis.’Gerundival attraction always appears after prepositions and when the gerund is in the dative. However, it is not impossible for it to appear in other cases, but is rarer.