Thousands more are reported trapped in a no-man's land between the violence at their backs and a frontier ahead of them.

VOA: standard.2010.06.15

Tangent means that it has the same slope, it just touches the efficient portfolio frontier for risky assets at one point, and the slope of the efficient portfolio frontier, including the riskless asset, is a straight line that goes through the tangency point, here.

相切意味着斜率相同，它与包含风险资产的有效边界,交与一点，而包含无风险资产的，有效边界，则是一条过切点的直线，切点在这里。

耶鲁公开课 - 金融市场课程节选

But if we have credit markets, then people can individually choose to be off the production possibility frontier and at a higher level of consumption than otherwise would.

但如果存在信贷市场,那么个人可以选择超越,PPF曲线的范围,达到比没有信贷市场时更高的消费水平

耶鲁公开课 - 金融市场课程节选