Hastings' Dictionary of the New Testament 
(Γάϊος = Caius, a Latin name, very common as a Roman praenomen)
1. In 1 Corinthians 1:14, a member of the Church of Corinth, baptized by St. Paul, who points out that in his case, as in the case of Crispus and in that of ‘the household of Stephanas,’ he thus deviated from his usual practice. Crispus was ‘the ruler of the synagogue’ ( Acts 18:8), and Gaius was presumably also a convert of some importance.
2. In Romans 16:23, a member of the Church of Corinth, whom St. Paul in the postscript to Romans calls his ‘host’ and the host of ‘the whole church,’ and whoso salutations are sent to the readers of the letter. He was evidently a man of position and means (the greeting from him immediately precedes that from Erastus, ‘the treasurer of the city’), whether his hospitality took the form of keeping open house for Christians and Christian visitors like the Apostle at Corinth or of allowing the Christians to meet for common worship and edification under his roof.
Everything points to the identification of 1 and 2. The same Gaius who was converted and baptized on St. Paul’s first visit to Corinth entertained him on his second visit. Now it is perhaps easier to believe that this Corinthian would have friends, whom he would wish to salute, at Ephesus rather than at Rome, and these salutations in Romans 16:23 are thought by some scholars to point to an Ephesian destination of the passage. But as Lightfoot remarks, in the Apostolic Church personal acquaintance was not necessary to create Christian sympathy ( Biblical Essays , 1893, p. 305).
3. In Acts 19:29, a companion of St. Paul, who with Aristarchus was seized at Ephesus. They are described as ‘men of Macedonia’ (Μακεδόνας), there being very little support for another reading, ‘a man of Macedonia,’ referring to Aristarchus only.
4. In Acts 20:4, a companion of St. Paul, who accompanied him from Greece to Asia Minor. He is described as ‘of Derbe’ (Δερβαῖος), possibly intentionally to distinguish him from 3.
Attempts have been made to identify 3 and 4. It is natural to do so, as the passages stand so close together. Emendations of the text have been suggested by which ‘of Derbe’ is taken with ‘Timothy,’ but these are purely conjectural, and Timothy was apparently a Lystran ( Acts 16:1-2). See W. M. Ramsay, St. Paul the Traveller and the Roman Citizen , 1895, p. 280.
5. In 3 John 1:1, the person to whom 3 John is addressed. He is described as ‘the beloved’ (ὁ ἀγαπητός), and is commended for his hospitality (v. 5). Nothing is known of this Gaius, and there is no reason to suppose him to have been any one of those of the same name associated with St. Paul.
T. B. Allworthy.
Bridgeway Bible Dictionary 
There are several people named Gaius in the New Testament, all except one of them connected with Paul. Paul baptized a man named Gaius in Corinth ( 1 Corinthians 1:14), and this was probably the person Paul stayed with on a later visit to Corinth ( Romans 16:23). Another person named Gaius was from Macedonia ( Acts 19:29) and another from Derbe ( Acts 20:4). According to a variation in some texts of Acts 20:4, this latter Gaius may have been from Thessalonica, in which case he was possibly the same person referred to in Acts 19:29.
Later in the first century, the apostle John wrote a letter to a friend named Gaius. He was a person noted for his strong faith, exemplary life, generous hospitality and sincere love ( 3 John 1:1-6).
Hastings' Dictionary of the Bible 
GAIUS . This name is mentioned in five places of NT. One Gaius was St. Paul’s host at Corinth, converted and baptized by him ( Romans 16:23 , 1 Corinthians 1:14 ). He was perhaps the same as ‘Gaius of Derbe’ who accompanied the Apostle from Greece to Asia ( Acts 20:4 ); if so, he would be a native of Derbe, but a dweller at Corinth. The Gaius of Macedonia, St. Paul’s ‘companion in travel’ who was seized in the riot at Ephesus ( Acts 19:29 ), and the Gaius addressed by St. John ( 3 John 1:1 ), were probably different men.
A. J. Maclean.
People's Dictionary of the Bible 
Gaius ( Gâ'Yus ). 1. A Macedonian, Acts 19:29, Paul's host at Corinth when the Epistle to the Romans was written, Romans 16:23, and baptized with his household by Paul. 1 Corinthians 1:14. He accompanied Paul to Ephesus, and was seized by the mob. Acts 19:29. The association of his name with that of Aristarchus seems to identify him with the Gaius of Derbe. Acts 20:4. Opinions differ on this point 2, To one of this name is addressed the third Epistle of John. 3 John 1:1.
Morrish Bible Dictionary 
1. Christian of Macedonia, and companion of Paul. He with Aristarchus was seized and carried into the theatre during the uproar at Ephesus. Acts 19:29 .
2. Convert of Derbe in Lycaonia, and companion of Paul. Acts 20:4 .
3. Christian at Corinth whom Paul baptised and who was his 'host' and of the whole church. Romans 16:23; 1 Corinthians 1:14 .
4. Convert of John, whose walk in the truth and in love was commended by the apostle, and to whom he addressed his third Epistle. 3 John 1 .
Fausset's Bible Dictionary 
Paul's host at Corinth when Paul wrote ( Romans 16:23), "mine host and of the whole church." Baptized by that apostle ( 1 Corinthians 1:14). The third epistle of John is addressed to "the well beloved" Gaius or Caius; probably the same, for he evidently had the means to do kindness "to the brethren and to strangers." He was converted through John ( 3 John 1:4-5). A Gaius of Macedonia is mentioned in Acts 19:29, and a Gaius of Derbe ( Acts 20:4); probably distinct men.
Easton's Bible Dictionary 
Bibliography Information Easton, Matthew George. Entry for 'Gaius'. Easton's Bible Dictionary. https://www.studylight.org/dictionaries/eng/ebd/g/gaius.html. 1897.
Holman Bible Dictionary 
Acts 19:29 Acts 20:4 3 Romans 16:23 1 Corinthians 1:14 3 John 1:1
International Standard Bible Encyclopedia 
gā´yus ( Γάΐος , Gáios ; Westcott and Hort, The New Testament in Greek , Gaı́os ):
(1) The Gaius to whom 3 Jn is addressed. He is spoken of as "the beloved" ( 3 John 1:1 , 3 John 1:2 , 3 John 1:5 , 3 John 1:11 ), "walking in the truth" ( 3 John 1:3 , 3 John 1:4 ), and doing "a faithful work" "toward them that are brethren and strangers withal" ( 3 John 1:5 , 3 John 1:6 ). He has been identified by some with the Gaius mentioned in the Apostolical Constitutions (VII, 46), as having been appointed bishop of Pergamum by John.
(2) Gaius of Macedonia, a "companion in travel" of Paul ( Acts 19:29 ). He was one of those who were seized by Demetrius and the other silversmiths in the riot at Ephesus, during Paul's third missionary journey.
(3) Gaius of Derbe, who was among those who accompanied Paul from Greece "as far as Asia," during his third missionary journey ( Acts 20:4 ). In the corresponding list given in the "Contendings of Paul" (compare Budge, Contendings of the Twelve Apostles , II, 592), the name of this Gaius is given as "Gallius."
(4) Gaius, the host of Paul when he wrote the Epistle to the Roman, and who joined in sending his salutations ( Romans 16:23 ). As Paul wrote this epistle from Corinth, it is probable that this Gaius is identical with (5).
(5) Gaius, whom Paul baptized at Corinth ( 1 Corinthians 1:14 ).
Cyclopedia of Biblical, Theological and Ecclesiastical Literature 
( Γάϊος , for Lat. Caius, a common Roman name), the name of three or four men in the N.T.
1. A Macedonian, and fellow-traveler of Paul, who was seized by the populace at Ephesus ( Acts 19:29), A.D. 54.
2. A man of Derbe (an epithet which some have very unnaturally transferred to Timothy) who accompanied Paul in his last journey to Jerusalem ( Acts 20:4), AD. 55.
3. An inhabitant of Corinth with whom Paul lodged, and in whose house the Christians were accustomed to assemble ( Romans 16:23; 1 Corinthians 1:14), A.D. 55. He was perhaps the same with one of the preceding.
4. A Christian (probably of Asia Minor) to whom John addressed his third epistle ( 3 John 1:1), A.D. cir. 92. (See Epistles Of John). There is no good reason for regarding him as identical with either of the foregoing (Wolf, Curae, ad loc.).
The Nuttall Encyclopedia 
A Roman jurist of the 2nd century, whose "Institutes" served for the basis of Justinian's.
- Gaius from Hastings' Dictionary of the New Testament
- Gaius from Bridgeway Bible Dictionary
- Gaius from Hastings' Dictionary of the Bible
- Gaius from People's Dictionary of the Bible
- Gaius from Morrish Bible Dictionary
- Gaius from Fausset's Bible Dictionary
- Gaius from Easton's Bible Dictionary
- Gaius from Holman Bible Dictionary
- Gaius from International Standard Bible Encyclopedia
- Gaius from Cyclopedia of Biblical, Theological and Ecclesiastical Literature
- Gaius from The Nuttall Encyclopedia