If a figure has four sides, then it is a quadrilateral; it cannot be a triangle.
A quadrilateral is a closed plane figure with four straight sides.
If it is a 2-dimensional figure then it is a quadrilateral. If it is a 3-dimensional figure then it is a tetrahedron.
A figure with 4 equal sides and 4 equal angles is a square :)
Square.
A four sided figure with no parallel sides is a trapezium, but it is also an irregular four-sided polygon, tetragon, quadrilateral, or quadrangle.
No plane figure has four vertices unless it has four sides.
A quadrilateral - if the sides are straight lines.
A four sided figure with four equal sides and no right angles is a diamond, or a rhombus. If it had four right angles, it would be a square.
Square
parallelogramrectanglesquare
A kite or an arrowhead