Removing a shell variable

Occasionally some stupid things come to mind. This is one of them.
Suppose we read a shell variable like this:

Code:

---

$ read a
12
$ echo $a
12

---

How can I delete this variable "a" now, without logging out or rebooting?

Thanks in advance.

"unset a" will get rid of it. Alternatively, "a=" will empty it so to all intents and purposes it's gone.

Thanks a lot!! :-D