Which is the meaning of root -vad- in words such as invade and evasive?

The root "-vad-" in words like "invade" and "evasive" comes from the Latin verb "vadere", which means "to go" or "to walk".

Here's how it breaks down:

* "Invade" - To "go into" or "enter" forcefully.

* "Evasive" - To "go away" or "avoid" something, often in a tricky or deceptive way.

Therefore, the "-vad-" root conveys the idea of movement, direction, or action in these words.