_A rhomboid is a parallelogram which has no right angle._ Name five other rhomboids. What three names may be given to Fig. 2? Why is it a quadrilateral? Why a parallelogram? Why a rhomboid? RHOMBS. Are the four sides of the rhomboid _a d_ equal to each other? Are the four sides of the rhomboid _e h_ equal to each other? If a triangle has its three sides equal to each other, what do you call it? Then when a rhomboid has its sides equal to each other, what may it be called? An equilateral rhomboid is called a rhombus. _A rhombus is an equilateral rhomboid._ See Note D, Appendix. Name two other rhombuses, or rhombs. What four names can you give to Fig. _e h_? Why a quadrilateral? Why a parallelogram? Why a rhomboid? Why a rhombus? RECTANGLES. Has the parallelogram _i l_ any right angles? How many? It is called a “_rectangle_.” _A rectangle is a right-angled parallelogram._ Name four other rectangles. What three names may be given to Fig. _i l_? Why a quadrilateral? Why a parallelogram? Why a rectangle? SQUARES. Has the rectangle _i l_ its four sides equal? Has the rectangle _m p_ its four sides equal? It is called a “square.” _A square is an equilateral rectangle._ Name another “_square_.” What four names may be given to Fig. _m p_? Why a quadrilateral? Why a parallelogram? Why a rectangle? Why a square? LESSON TWENTY-SEVENTH. REVIEW. Name six rhomboids. (DIAGRAM 21.) What three names may be given to Fig. 3? Why a quadrilateral? Why a parallelogram? Why a rhomboid? What is a quadrilateral? Parallelogram? Rhomboid? Name three rhombs. What four names may you give Fig. 5? Why a quadrilateral? Why a parallelogram? Why a rhomboid? Why a rhomb? What is a rhomboid? A rhomb? Name five rectangles. What three names may be given to Fig. 1? Why a quadrilateral? Why a parallelogram? Why a rectangle? What is a rectangle? Name two squares? By what four names may Fig. 7 be called? Why by the first? By the second? By the third? By the fourth? What is a square? What is a rectangle? What is a parallelogram? What is a quadrilateral? [Illustration: Diagram 22.] LESSON TWENTY-EIGHTH. COMPARISON AND CONTRAST. TRAPEZIUM AND TRAPEZOID. In what respect are Figs. A and B alike? On this account, what name may be given to each? How does Fig. B differ from Fig. A? What particular name may you give to Fig. B? What one to Fig. A? RHOMBOID AND RECTANGLE. In what two respects are Figs. C and D alike? On account of the number of their sides, what may each be called? Because their opposite sides are parallel, what may each be called?