Unless it is specified in a prayer, I say Holy Spirit…it makes more theological sense in English based on Aquinas’s explanation of why the Persons are named what they are named.
From his Summa Theologica:
"Firstly, from the fact that the person who is called “Holy Spirit” has something in common with the other Persons. For, as
Augustine says (De Trin. xv, 17; v, 11), “Because the Holy Spirit is common to both, He Himself is called that properly which both are called in common. For the Father also is a spirit, and the Son is a spirit; and the Father is holy, and the Son is holy.”
Secondly, from the proper signification of the name. For the name spirit in things corporeal seems to signify impulse and motion; for we call the breath and the wind by the term “spiritus”. Now it is a property of love to move and impel the will of the lover towards the object loved. Further, holiness is attributed to whatever is ordered to God. Therefore because the divine person proceeds by way of the love whereby God is loved, that person is most properly named “The Holy Spirit.” "
In English the term “spirit” can be synonymous with Enthusiasm, Ardor, and devotion…all of which are part of the reason why we call the Third Person the Holy Spirit…because as quoted above,
“it is a property of love to move and impel the will of the lover towards the object loved. Further, holiness is attributed to whatever is ordered to God. Therefore because the divine person proceeds by way of the love whereby God is loved”. He is called the Holy Spirit because he is the person of God who proceeds by way of Love of God. Now, “holy” means that which is ordered to God…and “spirit” means devotion, or enthusiasm. So the Person who proceeds as a term of God’s self-love is the Holy Spirit.
“ghost” in English has too many spooky conotations these days. But also, even more importantly, it has NO connotation of devotion or ardor…which is why the term “spiritus” is used in the first place…