'Empty' in the Bible

So it is with you, if you speak words [in an unknown tongue] that are not intelligible and clear, how will anyone understand what you are saying? You will be talking into the air [wasting your breath]!

and if Christ has not been raised, then our preaching is vain [useless, amounting to nothing], and your faith is also vain [imaginary, unfounded, devoid of value and benefit—not based on truth].