Square sails are square
Square sails are referred to as four-cornered sails.
Trapezoidal, actually. But the square sails were called square sails. Lateen or square could be referred to as yards.
"Square-riggers" have primarily square sails, but the jib sails are triangular.
"Square sails" which are not really square, were/are referred to as four-cornered sails.
Square sails (rectangular) were (are) called four-cornered sails.
Square sails are referred to as four-cornered 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.
They were referred to as "four-cornered" sails.
They are referred to as four-cornered sails.
They were referred to as "four-cornered" sails.
I'm not an expert, but I believe you can sail closer to the wind with a lateen-rigged sail than with square sails.