algebra

1. no quantity or number; naught; the figure 0.
5. a circumstance fact or influence that contributes to a result or outcome.
6. horizontal line on graphs
7. an activity or purpose natural to or intended for a person or thing.
11. the area of variation between upper and lower limits on a particular scale.
12. a way or manner in which something occurs or is experienced, expressed, or done.
13. arranged in or extending along a straight line
15. a simple way of representing statistical data on a plot in which a rectangle is drawn to represent the second and third quartiles, usually with a vertical line inside to indicate the median value.

2. the part of a plant which attaches it to the ground or to a support, typically underground, conveying water and nourishment to the rest of the plant via numerous branches and fibers.
3. vertical line on a graphs
4. based on or in accordance with reason or logic.
8. the state of wanting to know or learn about something or someone
9. intend to convey, indicate, or refer to (a particular thing or notion); signify.
10. not denoting, involving or arranged in a straight line.
14. to being the same in quantity and size and degree or value