42 CFR § 440.2 - Specific definitions; definitions of services for FFP purposes.
(a) Specific definitions.
Inpatient means a patient who has been admitted to a medical institution as an inpatient on recommendation of a physician or dentist and who—
(1) Receives room, board and professional services in the institution for a 24 hour period or longer, or
(2) Is expected by the institution to receive room, board and professional services in the institution for a 24 hour period or longer even though it later develops that the patient dies, is discharged or is transferred to another facility and does not actually stay in the institution for 24 hours.
Outpatient means a patient of an organized medical facility, or distinct part of that facility who is expected by the facility to receive and who does receive professional services for less than a 24-hour period regardless of the hour of admission, whether or not a bed is used, or whether or not the patient remains in the facility past midnight.
Patient means an individual who is receiving needed professional services that are directed by a licensed practitioner of the healing arts toward the maintenance, improvement, or protection of health, or lessening of illness, disability, or pain. (See also § 435.1010 of this chapter for definitions relating to institutional care.)
(b) Definitions of services for FFP purposes. Except as limited in part 441, FFP is available in expenditures under the State plan for medical or remedial care and services as defined in this subpart.