A postcaird or post caird is a rectangular piece o thick paper or thin cairdbuird intended for writin an mailing wioot an envelope. Thare hae been exceptions tae this, such as wuid postcairds, made o thin wuid, an copper postcairds sauld in the Copper Kintra o the U.S. state o Michigan.
In some places, it is possible tad send them for a lawer fee than for a letter. Stamp collectors distinguish atween postcairds (which require a stamp) an postal cairds (which hae the postage pre-printed on them). While a postcard is uisually printit bi a private company, individual or organization, a postal caird is issued bi the relevant postal authority.
The study an collectin o postcairds is termed deltiology.