Attributes of shapes are a major focus of geometry in grade one. Students can recognize shapes by their defining attributes: sides, angles, closed or not closed, etc. They also know what are not defining attributes: color, size, orientation, etc.
Students can compose and decompose shapes to form other shapes. For example, students can cut a rectangle into two triangles. As grade-one students partition circles and rectangles into two and four equal shares and use related language (halves, fourths, and quarters) they build an understanding of part-whole relationships and are introduced to fractional language. Fraction notation (¼, ½, ¾) will first be introduced in grade three. Students should be encouraged to note that cutting two different sized whole rectangles in half will result in different-size halves.