1-2.4 has a typo (minor) 

I found it in [here](http://grasshopperprimer.com/en/1-foundations/1-2/4_wiring-components.html):

> By default, a new connection will erase existing connections. Hold the SHIFT button while dragging connection wires to **difne** multiple sources. The cursor will turn green to indicate the addition behavior.

It should be **define** I think