"error"
A five letter word for a scientists mistake is "error."
error
error
error Fault
Five letter words with the second and fourth letter O are:boronbosomcocoacoloncolordonorhonormoronmotorrobotrotor
Delta
Iraqi
human
redye
Taken
Some five letter words with second letter O and fourth letter E are:bogeybowelbowercometcovencoverdowelhotellosermodelmowernoseynovelpowerrover
"Grade" is one word.