In NYT crosswords, the clue “vertical lines on graphs in math nyt” usually leads to Y-AXES. On coordinate graphs, the y-axis is the vertical axis, so the plural y-axes fits the clue’s wording and crossword style.
The term "vertical lines on graphs in math" usually alludes to asymptotes, or the lines that a curve approaches as it approaches infinity. The Y-AXIS, or the primary vertical line on a Cartesian coordinate plane, is another typical response.
