This code system http://hl7.org/fhir/basic-resource-type defines the following codes:

CodeDisplayDefinition
consentConsentAn assertion of permission for an activity or set of activities to occur, possibly subject to particular limitations; e.g. surgical consent, information disclosure consent, etc.
referralReferralA request that care of a particular type be provided to a patient. Could involve the transfer of care, a consult, etc.
adveventAdverse EventAn undesired reaction caused by exposure to some agent (e.g. a medication, immunization, food, or environmental agent).
aptmtreqAppointment RequestA request that a time be scheduled for a type of service for a specified patient, potentially subject to other constraints
transferTransferThe transition of a patient or set of material from one location to another
dietDietThe specification of a set of food and/or other nutritional material to be delivered to a patient.
adminactAdministrative ActivityAn occurrence of a non-care-related event in the healthcare domain, such as approvals, reviews, etc.
exposureExposureRecord of a situation where a subject was exposed to a substance. Usually of interest to public health.
investigationInvestigationA formalized inquiry into the circumstances surrounding a particular unplanned event or potential event for the purposes of identifying possible causes and contributing factors for the event
accountAccountA financial instrument used to track costs, charges or other amounts.
invoiceInvoiceA request for payment for goods and/or services. Includes the idea of a healthcare insurance claim.
adjudicatInvoice AdjudicationThe determination of what will be paid against a particular invoice based on coverage, plan rules, etc.
predetreqPre-determination RequestA request for a pre-determination of the cost that would be paid under an insurance plan for a hypothetical claim for goods or services
predeterminePredeterminationAn adjudication of what would be paid under an insurance plan for a hypothetical claim for goods or services
studyStudyAn investigation to determine information about a particular therapy or product
protocolProtocolA set of (possibly conditional) steps to be taken to achieve some aim. Includes study protocols, treatment protocols, emergency protocols, etc.