Origin: Latin prefix post-
Postcard has 3 different meanings across 1 category:
a card for sending messages by post without an envelope
"He slipped the short note into the pocket of his jacket to send it as a postcard from the beach."
A rectangular piece of thick paper or thin cardboard intended to be written on and mailed without an envelope. In the case of a picture postcard one side carries a picture or photograph.
"She bought a colorful picture postcard from the beach to send home as a souvenir."
In plain English: A postcard is a small card with space on both sides for writing messages and pictures that you mail without putting it inside an envelope.
"I kept a postcard from my trip to Paris on my desk."
Usage: A postcard is a small, stiff card designed to carry a brief message sent directly through the mail without needing an envelope. Unlike letters that require folding into paper wrappers, these cards are typically written on both sides and placed in a stamp slot for postage.
To send a postcard to.
"I decided to postcard my grandmother while I was visiting Paris."
The word is a straightforward combination of post and card. It entered English to describe a piece of paper intended specifically for mailing with the postage already paid on one side.