“Tranche”一词来源于法语，表示部分（slice/portion）。在投资领域，“tranche”指的是证券或债务的一部分，可以译为“层级”（class）。通常而言，债券、贷款、信用违约掉期（CDS）、住房抵押贷款支持证券（MBS）、资产支持证券（ABS）、担保债务凭证（CDO）等证券或债务会采取分层发行的方式，每个层级的风险等级不同。这些不同层级可以根据投资人预期的风险程度打包出售给投资人。层级的划分与以下风险因素有关：一是收益率，也就是投资的回报率；二是信用评级，用于评估借款人或债务或证券发行人的资信程度，信用评级越高，违约风险就越低；三是到期日，即证券或债务到期应归还投资人的日期。一般来说，低风险层级利率低但优先偿还，可出售给寻求相对安全投资的投资人，而高风险层级利率高但最后偿还，可出售给寻求高回报的投资人。这些层级包括优先级（senior tranche）、中间级（mezzanine tranche）和权益级（equity tranche）（或劣后级（junior tranche））。优先级风险最低，发生违约时对基础资产享有优先索取权，中间级次之，而权益级属于风险最高的层级。投资不同层级存在一定风险，尤其是高风险等级。比如，违约风险，证券或债务发行人无力支付；利率风险，即利率上升，证券或债务的价值就会下降；流动性风险，若有意购买证券的买家不多或者证券或债务市场交易量不大，则证券或债务难以出售。

例句：

Investors with various needs could invest in different tranches of the same collateralized mortgage obligation or mortgage-backed security. Let's say that we have four investors who want a similar mortgage-backed security but with different maturity dates. The portfolio could be split into tranches based on the maturity dates so that there would be tranches maturing in one year, five years, and 20 years. The investor who doesn't need access to cash anytime soon could invest in the 20-year tranche. However, the investors that are in retirement and need the cash in the short-term could opt for the one-year and two-year maturities. The investor who is in pre-retirement, meaning it's only five years away, could opt for the tranche with the five-year maturity.Tranches allow investors to structure their investment earnings and income to match their cash flow needs. Investors who need the cash sooner could buy a shorter maturity investment, while those who have a longer time horizon can invest in the longer-maturity tranches. Although investments can be broken up into tranches based on maturity and interest rates, they can also be grouped by domestic and international investments.

有不同需求的投资人可以对同一担保抵押债券或住房抵押贷款支持证券的不同层级进行投资。比如，现在有四位投资人，想要购买相似的住房抵押贷款支持证券，但是到期日不同。投资组合可以依据到期日拆分成多个层级，如一年期、五年期和二十年期。如近期无需取用现金，则可以选择二十年期。但是，如果投资人已退休，并且短期内需用现金，可以选择一年期和两年期。如果投资人临近退休，也就是说还有五年就退休，则可以选择五年期。就投资人而言，不同层级能够根据其现金流需求对投资收益进行规划。近期需要用现金的，可购买偿还期较短的层级；而可以接受较长投资期的，则可投资偿还期较长的层级。虽然投资组合能够按照到期日和利率拆分为多个层级，但国内外投资组合也可将其归为一组。