Exegesis:

ptoēthentes de kai emphoboi genomenoi ‘startled and terrified.’ For ptoeomai cf. on 21.9, for emphobos cf. on v. 5. There is little difference between the two and they serve to reinforce one another.

edokoun pneuma theōrein ‘they thought that they were looking at a ghost.’ For dokeō cf. on 8.18. pneuma (in this meaning †) means here ‘ghost,’ i.e. a bodyless being yet perceptible to the eye.

Translation:

Startled and frightened, or, “full of fear and terror” (Good News Translation), ‘very much frightened.’ For terms rendering the concept ‘fear’ see on 1.12.

Supposed, see on 2.44.

Spirit, or, ‘ghost,’ in the sense of that portion of the personality which leaves the body at death and is believed to appear to the living in bodily likeness.

Quoted with permission from Reiling, J. and Swellengrebel, J.L. A Handbook on the Gospel of Luke. (UBS Handbook Series). New York: UBS, 1971. For this and other handbooks for translators see here . Make sure to also consult the Handbook on the Gospel of Mark for parallel or similar verses.