What does ere mean in Elizabethan?

Shakespeare uses this Word twenty times in the play. You can substitute the Word "before" if you like. For example:

Let two more summers wither in their pride,

Ere we may think her ripe to be a bride.

means

Let two more summers wither in their pride,

Before we may think her ripe to be a bride.

Of course that makes the rhythm of the line wrong. Shakespeare did not use the Word "before" to refer to time, only to space. It is the opposite of "behind". So when Macbeth says, "Is this a dagger which I see before me?", he means that the dagger is in front of him spatially. When talking about a previous time, Shakespeare used the Word "ere".