lastChild

The designator lastChild refers to the last immediate child of the current note. For example:

                   I. A note

                                    Ia. Another Note

                                    Ib. Yet Another Note

                   II. Some Note

                                    IIc. Subsidiary stuff

                   III. Different stuff

                   IV. More Stuff

The lastChild of I is Ib. The lastChild of II is IIc. III has no lastChild.

The logical opposite of lastChild, i.e. the first child, is child [sic].

Using the optional child[N] notation, the equivalent of lastChild is child[-1]