In HTTP/2 specification, https://datatracker.ietf.org/doc/html/rfc7540, the following terminologies are used:

- client: The endpoint that initiates an HTTP/2 connection. Clients send HTTP requests and receive HTTP responses.

- connection: A transport-layer connection between two endpoints.

- connection error: An error that affects the entire HTTP/2 connection.

- endpoint: Either the client or server of the connection.

- frame: The smallest unit of communication within an HTTP/2 connection, consisting of a header and a variable-length sequence of octets structured according to the frame type.

- peer: An endpoint. When discussing a particular endpoint, "peer"refers to the endpoint that is remote to the primary subject of discussion.

- receiver: An endpoint that is receiving frames.

- sender: An endpoint that is transmitting frames.

- server: The endpoint that accepts an HTTP/2 connection. Servers receive HTTP requests and send HTTP responses.

- stream: A bidirectional flow of frames within the HTTP/2 connection.

- stream error: An error on the individual HTTP/2 stream.

Finally, the terms "gateway", "intermediary", "proxy", and "tunnel" are defined in Section 2.3 of [RFC7230]. Intermediaries act as both client and server at different times.

The terminology, connection error, is used in HTTP/2 specification, not in HTTP/1.1 specification. Because of that, it is considered new.