Saint is a word which has changed its meaning over the years. In the Bible it is a person who is 'set apart'-separated from his fellow men and women to work for God. In the Old Testament a man could chose to become a 'Nazirite' (q.v.), and to give his life to the service of God. He became a man 'set apart' or a 'saint'. To show his separateness, he avoided all the natural contaminations of daily life, did not drink wine, and allowed his hair to grow.
In the wider sense, all God's people are His 'saints' (see Psalm 85:8), once they have decided to serve Him. The angels are sometimes also referred to in this way (see Psalm 89:5-7; Daniel 8:13) because they exist to serve God (see Hebrews 1:7,14).

"Then the sovereignty, power and greatness of the kingdoms under the whole heaven will be handed over to the saints, the people of the Most High. His kingdom will be an everlasting kingdom, and all rulers will worship and obey Him." (Daniel 7:27).

No human authority can identify or appoint saints. "…God's solid foundation stands firm, sealed with this inscription: 'The Lord knows those who are His….'" (2 Timothy 2:19).