Short for mathematics - the logical study of quantity (numbers) and abstract structure (geometry), their operations, properties, applications, and how they all interrelate.
Aside from its incredible value in real-world applications (science, engineering, business, etc.), mathematics is also taught in schools because it's the best system to demonstrate and strengthen the vital concepts of deductive reasoning, objectivity, and abstract thinking.
People who are quick to say they hate math are typically those who had horrible math teachers/curricula in school, and never grasped the basic underlying concepts of math. Other reasons for an individual's poor math skills might include having a short attention span, no confidence to question what isn't understood, and the simple reinforcement by peers that it's OK to remain bad at math. But like a sonnet or a piece of sheet music, mathematics reveals its beauty to those who speak its language.
"No, YOU just suck at doing it."