en_tn_condensed/luk/24/37.md

But they were terrified

"But" indicates a strong contrast. Jesus told them to be at peace, but they were very afraid instead.

terrified and filled with fear

"startled and afraid." These two phrases mean about the same thing, and are used together to emphasize their fear. (See: rc://en/ta/man/jit/figs-doublet)

a spirit

Here it refers to the spirit of a dead person.