Difference Between Envy and Jealousy

Article from a bit back in time from Psychology Today here.

This is an interesting observation (looks true...):

Envy occurs when we lack a desired attribute enjoyed by another. 

Jealousy occurs when something we already possess (usually a special relationship) is threatened by a third person. 

And so envy is a two-person situation whereas jealousy is a three-person situation. 

Envy is a reaction to lacking something. Jealousy is a reaction to the threat of losing something (usually someone). This seems straightforward, and so why the confusion? 

One problem is an unfortunate semantic ambiguity with the word “jealousy” (but NOT with the word “envy”). If you ask people to describe a situation in which they felt jealous, they are as likely to describe an experience of envy (e.g., "I wished I had my friend's good looks") as of jealousy (e.g., "my girlfriend danced with an attractive guy"). Naturally, this creates a sense that jealousy and envy are very similar—even though they are actually quite different.

You need (at least?) 3 for jealousy and only 2 for envy... iow you can't have jealousy with only 2...

There are more than 2 USD Zombie nations out there... hmmmm....