first-order
/ˈfɜːstɔːdə(r)/adjective
1- of or relating to the simplest or most fundamental level of organization, experience, or analysis; primary or immediate（组织、经验或分析等的水平）最简单的; 最根本的; 最重要的; 直接的：
for a teacher, of course, drama must be a first-order experience.
对教师而言, 当然, 戏剧应当是一种直接的体验。
1.1
- technical having an order of one, especially denoting mathematical equations involving only the first power of the independent variable or only the first derivative of a function〈技〉一阶的, 一次的。