She is exceptionally knowledgeable in her field of expertise.

knowledgeable 是由名词 knowledge（知识）加上后缀 -able（能够...的）构成的形容词，意思是"知识渊博的、有见识的"。后缀 -able 表示"具有某种能力或特性"，所以 knowledgeable 字面意思是"具有丰富知识的"。