Diamarturomai is used for giving earnest testimony and for pressing a charge or warning upon hearers.

The term most often marks earnest testimony about a stated message, whether concerning Jesus, repentance and faith, the gospel, or a scriptural saying. It also occurs where a speaker presses an instruction or warning, including commands to avoid wrongdoing, partiality, useless quarrels, or coming judgment.

1. Earnestly affirming a message · dominant

   In Acts 18:5 the present participle accompanies Paul’s statement to the Jews that Jesus is the Christ, while Acts 20:21 places the same form with repentance toward God and faith toward the Lord Jesus. In Acts 20:24 the aorist infinitive names the stated aim of the ministry, and the APB renders the clause "to testify to the gospel of the grace of God."

   Acts 18:5Acts 20:21Acts 20:24Acts 23:11Acts 28:23Hebrews 2:6
2. Pressing a charge or warning · common

   In 1 Timothy 5:21 and 2 Timothy 4:1, first-person present forms stand in charges made in the presence of God and Christ Jesus. In 2 Timothy 2:14 the present participle accompanies a warning against useless quarrelling, and in Luke 16:28 the present subjunctive occurs in the request that someone warn five brothers against the place of torment.

   1 Thessalonians 4:61 Timothy 5:212 Timothy 2:142 Timothy 4:1Acts 2:40Luke 16:28

In the Anselm Project Bible: The APB commonly uses "testify" or "solemnly testifying," especially in statements of a message, but also renders the term’s context through "charge," "warn," and "bore witness and continued to exhort." These are verse-level renderings rather than fixed word-for-word equivalents.