HL7 & FHIR glossary

Short definitions of the terms you meet on interface tickets.

Term	Definition
ACK (acknowledgment)	A response message (often MSA) that says whether the receiver accepted, errored, or rejected what you sent. Source
ADT	Admit / Discharge / Transfer family of v2 messages (A01, A04, A08…). Source
Bundle (FHIR)	A package of resources: searchset, transaction, document, etc. Source
CodeableConcept	FHIR datatype for a concept that may carry several Codings plus text. Source
Control ID (MSH-10)	Unique id for one v2 message instance; echoed in MSA-2. Source
CX (extended composite ID)	v2 datatype for an identifier with assigning authority and type code. Source
DTM / TS	v2 date/time: digits YYYYMMDDHHMMSS with optional fractional seconds and ±ZZZZ. Source
FHIR	Fast Healthcare Interoperability Resources — HL7’s HTTP/JSON (or XML) standard for health data. Source
HL7 Version 2	Pipe-delimited messaging standard still dominant for hospital ADT/orders/results. Source
Identifier (FHIR)	Business id with a system URI and value (MRN, order number…). Source
Interface engine	Software that receives, filters, transforms, routes, and ACKs healthcare messages.
LOINC	Common coding system for lab and clinical observations (often OBX-3 / Observation.code). Source
MLLP	Minimal Lower Layer Protocol — the TCP framing usually used to carry v2 messages.
MRN	Medical record number — patient identifier type MR in v2 PID-3. Source
OperationOutcome	FHIR resource that explains errors/warnings from a server. Source
ORU	v2 unsolicited observation/result message type. Source
Patient (FHIR)	Demographics and administrative data for a person in care. Source
Processing ID (MSH-11)	P/T/D — which environment the message targets. Source
Resource (FHIR)	A typed unit of data with an endpoint, e.g. Patient, Observation. Source
Segment	One line of a v2 message starting with a three-character id (MSH, PID…). Source
Trigger event	The real-world event coded in MSH-9.2 (A04 registration, A08 update…). Source
US Core	U.S. FHIR implementation guide that profiles common resources. Source
XPN	v2 extended person name datatype (family^given^middle…). Source
XTN	v2 extended telecommunication number (phone/email components). Source