ADV
主要地;最重要地
You use chiefly to indicate that a particular reason, emotion, method, or feature is the main or most important one.
例句
He joined the consular service, chiefly because this was one of the few job vacancies...
他到领事馆工作，主要因为那是仅有的几个空缺职位之一。
His response to attacks on his work was chiefly bewilderment.
听到别人对自己工作的指责，他的反应主要是困惑。