总结以下内容，概括 refugee 和 displacement 的区别，并说明导致这些现象的主要原因。将总结限定在3句话之内。

"The phenomenon of displacement encompasses a broader set of people and situations, ranging from those uprooted by conflict or natural disasters to those on the move due to development projects. Displacement occurs within the same country, while refugees cross international borders. The primary causes of both displacement and refugee situations include conflict, war, natural disasters, and development projects. "
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displacement 涵盖了更广泛的人群和情况，包括因冲突、自然灾害或发展项目而流离失所的人，这些人可能在本国境内移动或迁移。refugee 特指那些因迫害、冲突等原因跨越国际边界寻求安全的人。导致这两种现象的主要原因有冲突、战争、自然灾害和发展项目。
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