# MessageChannel Glossary

Language for a private two-port pipe. Add a term only after it is in use, not as a reading list.

## Terms

**MessageChannel**:
The constructor that mints two MessagePorts and entangles them into one two-way pipe.
_Avoid_: named channel, broadcast channel, window channel

**entangled ports**:
A pair of MessagePorts such that a message posted on one is delivered only at the other.
_Avoid_: cloned ports, paired windows, channel name

**port (capability)**:
Holding a MessagePort is the permission to talk on that pipe. There is no `targetOrigin` on the send.
_Avoid_: window handle, origin check, named bus

**port message queue**:
The per-port mailbox that stores posts until they dispatch as `message` events. Born disabled.
_Avoid_: event buffer, paused listener

**start**:
Enables a port message queue. Implied by the first assignment to `onmessage`; required after `addEventListener("message")`.
_Avoid_: open, listen, resume

**close**:
Disentangles this port from its twin. Later posts find no target.
_Avoid_: pause, disable the queue

**transfer list**:
The extra argument (or `options.transfer`) that moves transferable objects instead of cloning them.
_Avoid_: clone list, payload

**event.ports**:
Frozen array of MessagePorts that arrived in the transfer list, in list order.
_Avoid_: event.data as the port

**detached**:
A transferable after transfer: the sender’s object is spent and cannot be used or transferred again.
_Avoid_: paused, closed, cloned

**DataCloneError**:
Thrown when structured clone cannot serialize a value, including a port that was not transferred or is already detached.
_Avoid_: TypeError, clone failure

**implicit port**:
The MessagePort a dedicated worker and its creator share. The page never holds the object; its port message queue is enabled at creation.
_Avoid_: Worker MessageChannel, default channel, worker origin

**connect port**:
The MessagePort a SharedWorker connection already has (`worker.port` / `onconnect` `event.ports[0]`).
_Avoid_: SharedWorker MessageChannel