Strong's 4342 (προσκαρτερέω)

attend (give self) continually (upon), continue (in, instant in, with), wait on (continually)

to be earnest towards, i.e. (to a thing) to persevere, be constantly diligent, or (in a place) to attend assiduously all the exercises, or (to a person) to adhere closely to (as a servitor)

from G4314 (πρός) and G2594 (καρτερέω);