• IPA: /ˈtɛstɪfaɪ/

testify (ambitransitive)

1. To make a declaration, or give evidence, under oath.
   • 2014, Ruzwana Bashir, "The untold story of how a culture of shame perpetuates abuse. I know, I was a victim ↗", The Guardian, 29 August 2014:

     It was only after a decade away from Skipton that I was finally able to garner the courage to return and testify against my abuser.

   • 1611, The Holy Bible, […] (King James Version), imprinted at London: By Robert Barker, […], OCLC 964384981 ↗, Numbers 35:30 ↗:

     One witness shall not testify against any person to cause him to die.

2. To make a statement based on personal knowledge or faith.
   • 1611, The Holy Bible, […] (King James Version), imprinted at London: By Robert Barker, […], OCLC 964384981 ↗, John 3:11 ↗:

     We speak that we do know, and testify that we have seen; and ye receive not our witness.

• bear witness

• attest
• testimony
• testimonial

• French: témoigner, attester
• German: bezeugen
• Portuguese: declarar, testemunhar
• Russian: свиде́тельствовать
• Spanish: testificar

• Portuguese: atestar
• Russian: свиде́тельствовать
• Spanish: atestiguar, aseverar