什么是 hard?Resistant to pressure; not readily penetrated.Physically toughened; rugged.Mentally toughened; strong-minded.Requiring great effort or endurance: a hard assignment. Performed with or marked by great diligence or energy: a project that required years of hard work. Difficult to resolve, accomplish, or finish: That was a hard question. Difficult to understand or impart: Physics was the hardest of my courses. Thermodynamics is a hard course to teach. Intense in force or degree: a hard blow. Inclement: a long, hard winter. Stern or strict in nature or comportment: a hard taskmaster. Resistant to persuasion or appeal; obdurate.Making few concessions: drives a hard bargain. Difficult to endure: a hard life. Oppressive or unjust in nature or effect: restrictions that were hard on welfare applicants. Lacking compassion or sympathy; callous.Harsh or severe in effect or intention: said some hard things that I won't forget. Bitter; resentful: No hard feelings, I hope. Causing damage or premature wear: Snow and ice are hard on a car's finish. Bad; adverse: hard luck. Proceeding or performing with force, vigor, or persistence; assiduous: a hard worker. Real and unassailable: hard evidence. Definite; firm: a hard commitment. Close; penetrating: We need to take a hard look at the situation. Free from illusion or bias; practical: brought some hard common sense to the discussion. Using or based on data that are readily quantified or verified: the hard sciences.