Skin tags that have changed color or bleed may require your doctor's evaluation and reassurance. Rarely, thrombosed skin tags may be a sign of another condition and need to be biopsied.
The x-axis and y-axis are two lines that create the coordinate plane. The x-axis is a horizontal line and the y-axis is a vertical line. I'm sure you've heard that a million times, but it might hard for you to remember which one is which. Here is a little trick to help you remember...
The y-axis on the wall is vertical but the one on the table is horizontal. In the 2-dimension case, as mentioned already, the usual designation of the vertical coincides with the y-axis in co-ordinate geometry.