Can you substitute vanilla extract and if so what is the exchange?

Vanilla extract or essence is added for concentrated flavour. Any substitute will therefore have a different flavour, but this can work well. Look for possibilities with concentrated flavour that won't alter the texture of the recipe. This may include alcohols such as rum, whiskey etc, or other flavouring essences. Consider the different flavours in the recipe and whether an alternative to vanilla would work with them. Eg: Chocolate cake with vanilla, could be changed to chocolate cake with orange essence or Grand Marnier: a different flavour, but just as nice.