Related Clues:

• The line y = 0, in math
• Horizontal line on a graph
• Graph line
• Bottom line?
• Horizontal base of a coordinate system
• Cartesian line
• Cartesian coordinate line
• Graph component
• It often represents time
• Horizontal graph line
• Line on which y = 0
• Horizontal line
• Graph of y = 0
• Graph basis
• Base line