expertness

noun

1. (uncountable, usually)The state of being expert; proficiency or skill.

   “I had […] armed myself with a revolver, in the use of which I finally reached a certain degree of expertness from frequent practice.”

   “Not only must she receive unheard-of personal favors and spiritual graces from her Saviour, but she must immediately write about them and exploiter them professionally, and use her expertness to give instruction to those less privileged.”