An invocation is a statement used during ritual, in order to invoke something. Invoking means to bring something inside of you. This is usually a god or goddess during Wiccan ritual, like during the Drawing Down the Moon, but it’s also been told that one might invoke a type of energy. When one invokes a god or goddess, it’s also called aspecting.
This is very different from an evocation. When we ask the deities to be present during ritual, it’s an evocation. Many people use the terms interchangeably, but they do not mean the same thing.
One way to remember the difference, is the first letter of the word. Invocation brings something to you internally, evocation, asks something to be present externally.
Invocations can be short and sweet, using modern language, or they could also be long and flowery, possibly even rhyming. There is a simple formula I learned from a book years ago, I believe it was Elements of Ritual by Deborah Lipp. Start your invocation out by naming the god/dess you are calling to, and being specific about it. Describe them. Then, make sure you praise Him or Her and let them know what you need from them.
Here’s a simple evocation of Demeter, utilizing this formula:
Beautiful earth goddess Demeter, mother of Persephone, whom we adore, please come unto us to witness this rite.
And a little more complex evocation:
Wife to Zeus,
Mother of Persephone,
Without whom the crops would not grow,
Honor us with your presence tonight,
And guide your daughters in their rite.
While either style of evocation will work, the more complex the evocation, I’ve found the more likely the chance that your goddess will show up. It also gives your ritual a little more formal flavor, and may help you connect more easily with the goddess of your choice.