先期 is a formal attributive word meaning 'earlier' or 'in advance', typically used in official, academic, or business contexts to describe something that happens before a planned or expected time. It often modifies nouns like 准备 (preparation), 投资 (investment), or 阶段 (stage). Unlike the more common adverb 先 (first), 先期 is more literary and is not used in everyday speech.