This root form (lemma) is used in 3 different forms in the NT: ἐπεστήριξαν (IAA3··P), ἐπιστηρίζοντες (PPA·NMP), ἐπιστηρίζων (PPA·NMS).
It is glossed in 2 different ways: ‘they strengthened them’, ‘strengthening’.
OET ACTS 14:22 Greek word=ἐπιστηρίζοντες (epistaʸrizontes) Morphology=PPA·NMP English gloss=‘strengthening’ SR GNT ACTS 14:22 word 1
OET ACTS 15:32 Greek word=ἐπεστήριξαν (epestaʸrixan) Morphology=IAA3··P English gloss=‘they strengthened them’ SR GNT ACTS 15:32 word 22
OET ACTS 15:41 Greek word=ἐπιστηρίζων (epistaʸrizōn) Morphology=PPA·NMS English gloss=‘strengthening’ SR GNT ACTS 15:41 word 13