When I try exercise 3 in 'Introduction to Form Validation in PHP' in Visual Studio, I get an error

I finished exercise 3 and then copied the code to clipboard, pasted it into a new file to test and it comes up with the error, " Notice : Undefined index: a-word in C:\xampp\htdocs\RainyDayBakes\test.php on line 15

"

Why is this?

difficult to say without seeing your code, please copy paste your code to the forum.