Synonyms of the word 
EXPERTNESS → EXPERTISE - SKILLFULNESS
expertness
- n. The state of being expert; skill or proficiency.
expertise
- n. Great skill or knowledge in a particular field or hobby.
- n. Advice, or opinion, of an expert.
skillfulness
- n. The state or quality of being adept or skillful.
If you are interested in words, visit the following sites :
- wiktionary.org/expertness For complete definition of a word
- 1word.ws/expertness to play with words, suffixs, prefixs, etc.