This root form (lemma) is used in 3 different forms in the NT: φθέγγεσθαι (NPM····), φθεγγόμενοι (PPM·NMP), φθεγξάμενον (PAM·NNS).
It is glossed in 3 different ways: ‘having spoken’, ‘to_be speaking’, ‘speaking’.
OET ACTS 4:18 Greek word=φθέγγεσθαι (fthengesthai) Morphology=NPM···· English gloss=‘to_be speaking’ SR GNT ACTS 4:18 word 17
OET 2PET 2:16 Greek word=φθεγξάμενον (fthegxamenon) Morphology=PAM·NNS English gloss=‘having spoken’ SR GNT 2PET 2:16 word 12
OET 2PET 2:18 Greek word=φθεγγόμενοι (fthengomenoi) Morphology=PPM·NMP English gloss=‘speaking’ SR GNT 2PET 2:18 word 5