42 CFR § 413.333 - Definitions.

---
identifier: "/us/cfr/t42/s413.333"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "42 CFR § 413.333 - Definitions."
title_number: 42
title_name: "Public Health"
section_number: "413.333"
section_name: "Definitions."
chapter_name: "CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF HEALTH AND HUMAN SERVICES"
subchapter_number: "B"
subchapter_name: "MEDICARE PROGRAM"
part_number: "413"
part_name: "PRINCIPLES OF REASONABLE COST REIMBURSEMENT; PAYMENT FOR END-STAGE RENAL DISEASE SERVICES; PROSPECTIVELY DETERMINED PAYMENT RATES FOR SKILLED NURSING FACILITIES; PAYMENT FOR ACUTE KIDNEY INJURY DIALYSIS"
positive_law: false
currency: "2026-03-24"
last_updated: "2026-03-24"
format_version: "1.1.0"
generator: "[email protected]"
authority: "42 U.S.C. 1302, 1395d(d), 1395f(b), 1395g, 1395l(a), (i), and (n), 1395m, 1395x(v), 1395x(kkk), 1395hh, 1395rr, 1395tt, and 1395ww."
regulatory_source: "51 FR 34793, Sept. 30, 1986, unless otherwise noted."
cfr_part: "413"
---


# 413.333 Definitions.

As used in this subpart—

*Case-mix index* means a scale that measures the relative difference in resource intensity among different groups in the resident classification system.

*Market basket index* means an index that reflects changes over time in the prices of an appropriate mix of goods and services included in covered skilled nursing services.

*Resident classification system* means a system for classifying SNF residents into mutually exclusive groups based on clinical, functional, and resource-based criteria. For purposes of this subpart, this term refers to the current version of the resident classification system, as set forth in the annual publication of Federal prospective payment rates described in § 413.345.

*Rural area* means, for services provided on or after July 1, 1998, but before October 1, 2005, an area as defined in § 412.62(f)(1)(iii) of this chapter. For services provided on or after October 1, 2005, *rural area* means an area as defined in § 412.64(b)(1)(ii)(C) of this chapter.

*Urban area* means, for services provided on or after July 1, 1998, but before October 1, 2005, an area as defined in § 412.62(f)(1)(ii) of this chapter. For services provided on or after October 1, 2005, *urban area* means an area as defined in §§ 412.64(b)(1)(ii)(A) and 412.64(b)(1)(ii)(B) of this chapter.

[63 FR 26309, May 12, 1998; 63 FR 53307, Oct. 5, 1998, as amended at 73 FR 46440, Aug. 8, 2008; 82 FR 36633, Aug. 4, 2017]