Are all believers "saints" or are saints a special class?

Will you please explain the meaning of the term “Saints”? Does It apply to all believers?

A saint is one who is sanctified and the root meaning of the Hebrew and Greek words, translated “Sanctify,” is to set apart for a particular Purpose, the nature of which is not specified. It may be good, it may even be bad. Perhaps Psalm 4:3 is one of the best definitions of scriptural sanctification: “But know that the Lord hath set apart him that is godly for himself. The word, “godly”, being a descriptive title of  the people of God—those who belong to God. Compare Psalm 50:5:
“Gather my saints together unto Me, those that have made a covenant with me by sacrifice.” This includes all the people of God. Holiness of conduct is clearly the end in view, but we must not confuse the way and the destination. We get into great confusion if we forget this distinction, that sanctification does not in itself denote a change of character or conduct, but that in some cases it leads to that.

(1) Thus, “sanctify”, is applied to inanimate objects, which cannot experience a change of character—e.g., the gold sanctified by the temple and the gifts by the altar (Matthew 23:17-18).
(2) It is applied to unconverted persons, whose character presumably remains unchanged. The unbelieving husband is sanctified by the wife and unconverted children by the parents (1 Corinthians 7:4).
(3) It is applied to the Lord who never needed a change of character. “Say ye of Him whom the Father hath sanctified and sent into the world.” “For their sakes I sanctify myself” (John 10:36; John 17:19).

Progressive sanctification is the continued response of the believer, whom God has set apart, to His purpose for him. Joseph was set apart by Pharaoh to rule Egypt, so he did not go back to the prison but gave himself to the work. Paul was set apart for God’s service and he was “not disobedient unto the heavenly vision.” If God has sanctified us at the moment of our conversion, it is for us to sanctify ourselves, and this will undoubtedly shew itself in our conduct. It is a very sad thing when believers can talk of sanctification and yet are but little sanctified in their ways. True sanctification consists in conforming our ways to what God has revealed in His Word for us. The Scriptures meditated upon are a great means in the hands of the Spirit for sanctifying the people of God (John 17. 17).