third party

third-party的词性：
n.（名词）

1. A political party organized as opposition to the existing parties in a two-party system.
第三党：在两党制下与现存的两党派相对立而建立的一个政党

2. One other than the principals involved in a transaction:
第三者：在一次交易中交易人之外的另一个人：

I pay rent to a third party, not directly to the landlord.
我把房租交给第三者，没有直接交给房主