在甲壳类，十足目（特别是长尾亚目）头胸甲前端向前方突出的一个剑状突起，略呈三角形，背腹或左右扁平，外缘多具尖锐的锯齿。因种类不同，有的是很长的。额剑的功能尚不明确。
额隐窝过度发育导致其一与额窦的解剑关系复杂和多变，是手术的难点。
The volume recessus grows excessively causes its one to relate with frontal sinus's Xie Jian is complex and is changeable, is surgery's difficulty.
因赊销行为引起的应收账款是一把双刃剑，它在提高销售额和增加利润的同时，也会给企业带来风险和成本。
Account receivable caused by credit is a double-blade sword because it improve sales volume and profit as well as bring about risks and cost for enterprises.
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