1. 四边形   quadrilateral   heptagon   ray   quadrangle   Hint Half-n-half Clue   2. 多角形   edge   vertex   polygon   hexagon   Half-n-half Clue   3. 七边形   concave   hexagon   heptagon   polygon   Half-n-half Clue   4. 六角形   hexagon   oval   quadrilateral   prism   Half-n-half Clue   5. 棱镜   rhombus   parallel lines   edge   prism   Half-n-half Clue   6. 四方形   quadrilateral   hexagon   pyramid   heptagon   Half-n-half Clue   7. 凹面   vertex   concave   hemisphere   hexagon   Half-n-half Clue