common

—happening often；existing in large numbers or in many places常见的，普遍的

—belonging to or shared by two or more people 共有的，共享的，共同的

—ordinary and not special 普通的，平凡的，平常的

ordinary

—not different or special普通的，平凡的，平常的（与common同义）

—not particularly good or impressive 平淡无奇的（反义词：extraordinary）

normal

—Something that is normal is usual and ordinary, and is what people expect. 正常的; 平常的

—A normal person has no serious physical or mental health problems. 身心正常的

usual

—to describe what happens or what is done in most of the time or in most cases (形成习惯的)通常的， 惯常的，平常的