"Square-riggers" have primarily square sails, but the jib sails are triangular.
caravel
A caravael
Square sails are square
Sloops, ketches, and yawls have triangular-shaped sails.
the caravel has triangular sails as well as square sails. Square sails carried the ship forward when the wind was at its back. Triangular sails allowed the caravel to sail into the wind. the caravel was better than other euoopean ships of the time at this type of sailing
a ship with triangular sails that allowed it to sail into the wind and with square sails that carried it forward when the wind was at it's back.
Trapezoidal, actually. But the square sails were called square sails. Lateen or square could be referred to as yards.
Square sails (rectangular) were (are) called four-cornered sails.
They were referred to as "four-cornered" sails.
A clipper.
Square sails are not truly square but rectangular with a longer long side on the bottom perimeter of the sail. They were and are referred to as "four-cornered" sails.