Square sails are square
Either a marconi or lanteen rig
Lanteen sails are still made
"Square-riggers" have primarily square sails, but the jib sails are triangular.
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.
caravel
caravel
Lanteen sails
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.
A caravael
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