When in doubt, defer to the official spec: https://hl7.org/fhir/.
| Term | Definition | |
|---|---|---|
| Base URL | The root URL of a FHIR server (e.g. http://localhost:8080/fhir) that all endpoints are relative to | |
| Batch | A Bundle.type=batch processed per-entry (partial success is expected) | |
| Bundle | An envelope for multiple resources (search, batch, transaction, …) | |
| Bundle.entry | One item inside a bundle; for search it holds a resource, for batch/transaction it also carries a request and response | |
| Canonical URL | Stable identifier for conformance resources (profiles, extensions, ValueSets) | |
| CapabilityStatement | The server’s self-description returned by GET [base]/metadata (supported resource types, interactions, search params, operations) | |
Choice type (value[x]) | A polymorphic element where the datatype is chosen from a defined set (e.g. valueString, valueQuantity, …). The [x] is replaced with the capitalized type name. | |
| CodeSystem | Defines a set of codes (the “universe” a Coding.system points to) | |
| CodeableConcept | A datatype for human-friendly coded concepts (multiple coding[] plus optional text) | |
| Coding | A datatype representing one code from one system (system, code, optional display) | |
| Compartment | A standardized way to scope data “related to” an instance (e.g. /Patient/123/Observation) | |
| ConceptMap | A resource that defines mappings/translations between code systems (often used with $translate) | |
| Conditional create | Create only if no match exists, usually using If-None-Exist: <criteria> | |
| Conditional delete | Delete a single match selected by search criteria (fails if ambiguous) | |
| Conditional update | Update a single match selected by search criteria (fails if ambiguous) | |
| Conformance resources | Resources that describe rules/capabilities (e.g. StructureDefinition, ValueSet, SearchParameter, OperationDefinition) | |
| Contained resource | A resource embedded in another resource under contained[] without its own REST identity (referenced as #id) | |
| Datatype | The defined type of an element (primitive like date or complex like HumanName, Identifier, Reference) | |
| Differential | The “delta” view of a profile: only the constraints that differ from the base definition | |
| Element | A named field in a resource/datatype (e.g. Patient.name, Observation.status) with defined rules (type, cardinality, bindings) | |
| ETag | HTTP header used for version-aware concurrency; typically W/\"<versionId>\" in FHIR responses | |
| Extension | A standard mechanism to add data not in the base model, anchored by a canonical url | |
| FHIRPath | An expression language for navigating resources, used in invariants and definitions | |
| fullUrl | A Bundle entry identifier used to reference resources within a bundle (commonly urn:uuid:... in transactions) | |
| History | Past versions of resources, typically via GET [base]/{type}/{id}/_history | |
| Identifier | A business identifier (MRN, external ids), searched via `identifier=system | value` |
| IG (Implementation Guide) | A published specification that profiles FHIR for a specific use case (e.g. US Core, IPS). Typically distributed as a FHIR package containing profiles, extensions, terminology, and examples. Also refers to the ImplementationGuide resource type that describes the IG’s structure. | |
| IG Publisher | A JAVA tool from HL7 to take a set of inputs and create a standard FHIR IG. | |
| If-Match | HTTP header used for version-aware updates (“only update if current version matches this ETag”) | |
| Interaction | A REST action like read, create, search-type | |
| Invariant | A rule (often FHIRPath) that must hold for a resource/element (declared in a profile) | |
| Logical id | The id used in URLs (Patient/123) | |
| meta | Server-managed metadata such as versionId, lastUpdated, profile[], tag[], security[] | |
| meta.profile | Declares which profiles an instance claims conformance to (used by validators/servers) | |
| meta.tag | Labels for workflow/categorization (not access control) | |
| meta.security | Security labels used for confidentiality and access-control decisions in some ecosystems | |
| modifierExtension | An extension that changes interpretation; consumers must not ignore it | |
Narrative (text.div) | Human-readable HTML summary of a resource; not a substitute for structured data | |
| Operation | A $-prefixed procedure beyond REST interactions (e.g. $expand) | |
| OperationDefinition | Describes an operation’s inputs/outputs and invocation level (system/type/instance) | |
| OperationOutcome | Standard error/reporting resource returned on failures (and sometimes warnings) | |
| Parameters | The resource used as input/output for operations (named parameter[] values) | |
| Package | A distributable collection of conformance resources (often an IG) in the FHIR package format | |
| Primitive type | A scalar datatype like string, boolean, date, dateTime, code (often represented as JSON primitives) | |
| Profile | Constraints for a resource type (StructureDefinition) | |
| Reference | A pointer to another resource (relative Patient/123, absolute URL, or other reference patterns) | |
| resourceType | The required top-level field that declares what kind of resource a JSON object is (Patient, Observation, …) | |
| Resource | A typed JSON document like Patient | |
| SearchParameter | Defines a search name, type (token/string/date/…), and expression over resources | |
| Snapshot | The fully expanded view of a profile after applying base + constraints (often generated from a package) | |
| Slicing | A way to impose different rules on different “slices” of a repeating element (e.g. specific identifier slices) | |
| System | code | Common “token” search form combining a coding system and code (e.g. `code=http://loinc.org | 29463-7`) |
| Terminology | Coded values and their rules (ValueSet, CodeSystem) | |
| Terminology binding | A rule that ties a coded element to a ValueSet with a strength (required, extensible, preferred, example) | |
| Transaction | A Bundle.type=transaction processed atomically (all-or-nothing) | |
| ValueSet | Defines which codes are allowed for an element (a subset/selection from one or more CodeSystems) | |
| vread | Versioned read: fetch a specific version via GET [base]/{type}/{id}/_history/{vid} | |
| versionId | meta.versionId, the logical version identifier used for history and concurrency control | |
| lastUpdated | meta.lastUpdated, the timestamp the server last updated that version of the resource |
Next
- Data basics: Resources
- How requests work: CRUD, Search
- Multi-request writes: Batch & Transaction