### Question
Can you define what retirement system means?


### Answer
**Retirement system** is defined as the following in *26 U.S.C. § 3121*:

> given such term by section 218(b)(4) of the Social Security Act;

#### Citation:
  - *26 U.S.C. § 3121*
  - Heading: **Subtitle C-Employment Taxes > CHAPTER 21-FEDERAL INSURANCE CONTRIBUTIONS ACT > Subchapter C-General Provisions**

