Extract vs essence vs oil: can you use them interchangeably? Is there any kind of formula for substituting them with each other?

I order them from King Arthur Flour. I think you can get a larger individual bottle of the lemon, but I order the box of three--one ounce each of lemon, lime and orange.

That sounds interesting, Jean. Where do you find these citrus oils?

In US we say extract, in UK they say essence. Oils, however, are another matter entirely. I use pure citrus oils (they come in 1-ounce bottles) and I use them *sparingly*! They are very concentrated. It takes the oil from the rinds of 66 lemons to fill a 1-ounce bottle. If a recipe calls for the zest of one lemon, you might use 1/8 teaspoon of the oil. Hope this helps!
Jean | Delightful Repast | http://delightfulrepast.com

to my experience, extract and essence are pretty in-exact terms. You need to look and see what the base is to know what you're dealing with, but for the most part concentrated extracts or essences or oils are all relatively interchangable, but you may need to change the proportions depending on the exact product you've got. FWIW, I have found that the 'oils' I've run into don't really have the punch the alcohol-based extracts do.

This link should help: http://www.foodsubs.com/Extracts.html