13 But since concerning spirit in general many diverse things are written in the divine Scriptures, and there is fear lest some out of ignorance fall into confusion, not knowing to what sort of spirit the writing refers; it will be well now to certify you, of what kind the Scripture declares the Holy Spirit to be. For as Aaron is called Christ, and David and Saul and others are called Christs, but there is only one true Christ, so likewise since the name of spirit is given to different things, it is right to see what is that which is distinctively called the Holy Spirit.
For many things are called spirits. Thus an Angel is called spirit, our soul is called spirit, and this wind which is blowing is called spirit; great virtue also is spoken of as spirit; and impure practice is called spirit; and a devil our adversary is called spirit. Beware therefore when you hear these things, lest from their having a common name thou mistake one for another. For concerning our soul the Scripture says, His spirit shall go forth, and he shall return to his earth: and of the same soul it says again, Which forms the spirit of man within him. And of the Angels it is said in the Psalms, Who makes His Angels spirits, and His ministers a flame of fire. And of the wind it says, You shall break the ships of Tarshish with a violent spirit; and, As the tree in the wood is shaken by the spirit; and, Fire, hail, snow, ice, spirit of storm. And of good doctrine the Lord Himself says, The words that I have spoken unto you, they are spirit, and they are life; instead of, “are spiritual.”
But the Holy Spirit is not pronounced by the tongue; but He is a Living Spirit, who gives wisdom of speech, Himself speaking and discoursing.
Source: Catechetical Lectures (New Advent)