From BiblePortal Wikipedia

Hastings' Dictionary of the New Testament [1]

(Τέρτιος, a Latin name)

Tertius is the amanuensis of St. Paul who in  Romans 16:22 interposes a greeting in his own name to the Apostle’s readers, ‘I Tertius, who write the epistle, salute you in the Lord’ (Revised Version), or possibly, ‘I Tertius salute you, who write the epistle in the Lord’ (ἀσπάζομαι ὑμᾶς ἐγὼ Τέρτιος ὁ γράψας τὴν ἐπιστολὴν ἐν κυρίῳ). That St. Paul generally dictated his letters and added a few words in his own handwriting is clear from  1 Corinthians 16:21,  Galatians 6:11,  Colossians 4:18,  2 Thessalonians 3:17, and probably  Philemon 1:19. The amanuensis no doubt took down the Apostle’s words in shorthand, which was extensively used at the time, and later wrote out the letter for transmission (the employment of different amanuenses has been thought to account to some extent for the considerable diversity of style in the Pauline Epistles; see Sanday-Headlam, International Critical Commentary , ‘Romans’4, 1900, p. lx). Then St. Paul took up the pen and authenticated the letter, thus guarding against the palming off of forged documents under his name. Other postscripts of this kind have been suspected in the doxology ( Romans 16:25-27) and in  2 Corinthians 13:11ff.,  Philippians 4:21 ff.,  1 Thessalonians 5:25ff. All this was quite in accordance with the custom of the time. If we can suppose, with some, that the ‘stake in the flesh’ from which the Apostle suffered was ophthalmia, or that he was unfamiliar with the use of the pen owing to his manual labour of tent-making, there would seem to be sufficient reason for St. Paul following the custom. Nothing further is known of Tertius. It is quite as unlikely that St. Paul kept a regular secretary as that Tertius was a slave whom he hired to do the work. He must have been a faithful attendant and companion of the Apostle, who, whether the alternative rendering given above be correct or not, ‘wrote the epistle in the Lord,’ i.e. as a Christian, in a spirit of loving service (see G. Milligan, Thessalonians , 1908, Note A, p. 124 ff.). His personal salutation does not necessarily imply that he was known to those to whom the letter was directed. If its destination was Rome, it is just possible that, as he bears a Latin name and was perhaps a Roman, he may have had friends among those whom the Apostle greets. If we suppose that the salutations were sent to Ephesian Christians, we may conjecture that Tertius had met many of them on the missionary journeys on which he may have accompanied St. Paul.

T. B. Allworthy.

Hastings' Dictionary of the Bible [2]

TERTIUS . St. Paul’s amanuensis who wrote Romans and added a personal salutation (  Romans 16:22 ). It was the Apostle’s custom to employ a scribe (no doubt dictating shorthand notes, a common practice), but to add a short autograph himself. The autographs probably are:   Romans 16:25-27 ,   1 Corinthians 16:21-24 (expressly),   2 Corinthians 13:13 f.,   Galatians 6:11-18 (expressly),   Ephesians 6:23 f.,   Philippians 4:21-23 ,   Colossians 4:18 (expressly),   1 Thessalonians 5:25-28 ,   2 Thessalonians 3:17 f., (expressly). In the Pastoral Epistles and Philemon, which are personal letters, the presence of autograph passages is more uncertain.

A. J. Maclean.

Fausset's Bible Dictionary [3]

Paul's Amanuensis in writing the epistle to the Romans ( Romans 16:22) from Corinth. His greeting inserted in the middle of Paul's greetings to the Romans shows that he was well acquainted with the Roman Christians, "I Tertius, who wrote this epistle, salute you in the Lord"; his name too makes it likely he was a Roman.

Smith's Bible Dictionary [4]

Ter'tius. (Third). Probably a Roman, was the amanuensis, [A person whose employment is to write what another dictates.], of Paul in writing the Epistle to the Romans.  Romans 16:22. (A.D. 55).

Hawker's Poor Man's Concordance And Dictionary [5]

This man hath honourable mention made of him in Scripture, from his services to the Apostle Paul. ( Romans 16:22)

Morrish Bible Dictionary [6]

The Christian who wrote the Epistle to the Romans at Paul's dictation, and who sent his own salutation to the saints.  Romans 16:22 .

American Tract Society Bible Dictionary [7]

A Christian whom Paul employed as his amanuensis in writing the epistle to the Romans,  Romans 16:22 .

Holman Bible Dictionary [8]

 Romans 16:22 Romans 16:23

Easton's Bible Dictionary [9]

 Romans 16:22

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [10]

( Τέρτιος , Graecized from the Lat. Tertius, Third; Vulg. Tertius) was the amanuensis of Paul in writing the Epistle to the Romans (16, 22). A.D. 55. He was at Corinth, therefore, and Cenchrese, the port of Corinth, at the time when the apostle wrote to the Church at Rome. It is noticeable that Tertius intercepts the message which Paul sends to the Roman Christians, and inserts a greeting of his own in the first person singular ( Ἀσπάζομαι Ἐγὼ Τέρτιος ). Both that circumstance and the frequency of the name among the Romans may indicate that Tertius was a Roman, and was known to those whom Paul salutes at the close of the letter. Secundus ( Acts 20:4) is another instance of the familiar usage of the Latin ordinals employed as proper names. The idle pedantry (indulged in by Burmann, Exercit. Theol. 2, 161 sq.) which would make him and Silas the same person because Tertius and שְׁלַישַׁי mean the same in Latin and Hebrew, hardly deserves to be mentioned (see Wolf,. Curae Philologicae, 3, 295); and equally idle is Roloffs conjecture (De Trib. Nomin. Pauli [Jen. 1731]) and Storck's (Exercit. de Tertio, in the Fortges. niutzl. Samml. p. 23) that Tertius is but a pseudonym for Paul himself. In regard to the ancient practice of writing letters from dictation, see Becker's Gallus, p. 180. No credit is due to the writers who speak of him as bishop of conium (see Fabricius, Lux Evangelica, p. 117). Smith. See also Briegleb, De Tertio (Jen. 1754); Eckhard, De Signo Pauli (Viteb. 1687); Hertzog, De Subscriptionibus Pauli (Lips. 1703). (See Paul).

International Standard Bible Encyclopedia [11]

tûr´shi - us ( Τέρτιος , Tértios ): The amanuensis of Paul who wrote at his dictation the Epistle to the Romans. In the midst of Paul's greetings to the Christians in Rome he interpolated his own, "I Tertius, who write the epistle, salute you in the Lord" (  Romans 16:22 ). "It is as a Christian, not in virtue of any other relation he has to the Romans, that Tertius salutes them" (Denney). Some identify him with Silas, owing to the fact that shālı̄sh is the Hebrew for "third (officer)," as tertius is the Latin Others think he was a Roman Christian residing in Corinth. This is, however, merely conjecture. Paul seems to have dictated his letters to an amanuensis, adding by his own hand merely the concluding sentences as "the token in every epistle" (  2 Thessalonians 3:17;  Colossians 4:18;  1 Corinthians 16:21 ). How far this may have influenced the style of his letters is discussed in Sanday-Headlam, Romans , Introduction, LX.

Kitto's Popular Cyclopedia of Biblial Literature [12]

Ter´tius. We learn from ('I Tertius, who wrote this epistle, salute you in the Lord'), that the Apostle Paul dictated that epistle to Tertius. Some writers say that Tertius was bishop of Iconium.