2. How to read multi-digits: first grade the multi-digits, and then count down from the high position; When reading hundreds of millions or tens of thousands of numbers, add the word "hundred million" or "ten thousand" at the back; The zeros at the end of each stage are not read, and other numbers have one or several zeros and only one zero is read;

3. Multi-digit writing: write from a high position and write down one level at a time according to the sequence table; There is no unit on any number, just write 0 on that number;

4. You can draw countless rays from one point; You can draw countless straight lines after a point; Only one straight line can be drawn after two o'clock;

5. Two straight lines that do not intersect in the same plane are called parallel lines, or they are parallel to each other. If two straight lines intersect at right angles, they are said to be perpendicular to each other, one of which is called the perpendicular of the other, and the intersection of these two straight lines is called the vertical foot;

6. If two straight lines are parallel to the third straight line, then the two straight lines are also parallel to each other. If both lines are perpendicular to the third line, then the two lines are parallel to each other.