OBJECTIVE - G.CO.A.1
Know precise definitions of angle, circle, perpendicular line, parallel line, and line segment, based on the undefined notions of point, line, distance along a line, and distance around a circular arc.
INTERPRETATION OF OBJECTIVE - G.CO.A.1
This is not a one time teachable objective. This objective is basically telling us that when you introduce new vocabulary to class, define it precisely. This objective would often work in conjunction with the other objectives throughout the year.
One thing that is specific to now, at the beginning of the year is the discussion of undefined terms. Students need to understand the difference between a definition and a representation.