Expert
Part of speech: adjective
Definition: Extraordinarily capable or knowledgeable. Characteristic of an expert.
Part of speech: noun
Definition: A person with extensive knowledge or ability in a given subject. A player ranking just below master.
Proficient
Part of speech: adjective
Definition: Good at; skilled; fluent; practiced, especially in relation to a task or skill.
Part of speech: noun
Definition: An expert.
Example sentence: If we do not get No Child Left Behind right for Limited English Proficient students, the law will be a failure for most schools in the 15th Congressional District, and for many across the nation.