teacher, lecturer, instructor这三个词有什么区别？

teacher(n.) 教师、教员（以教书为职业的人）

Teacher is the general term for someone whose job is to teach. There are many kinds of teachers, primary school teachers, high school teachers and university teachers.

For example:
I'd like to go into teaching and get a job as a teacher in an inner city primary or secondary school.

lecturer(n.) 大学讲师、讲课者、授课者

A lecturer is someone who gives a lecture or formal presentation, particularly at a college or university.

For example:
Dr. Gradgrind is our lecturer on the Victorian novel and the course will be taught through a series of lectures and seminars.

Please note: A seminar at a college or university is a class for a small group of students to discuss the subject with the lecturer.

instructor(n.) 教练、教员；(美)大学讲师
In British English, an instructor teaches you on how to learn or improve in a particular skill or sport.

for example:
If you want to learn how to drive, you will need a driving instructor.
If you want to learn how to fly, you will require a flying instructor.

Please note: In the US, an instructor is a university teacher below the rank of assistant professor.

teacher
n.教师（以教书为职业的人)
lecturer n.演讲者, 讲师
instructor
n.教师, <美>讲师

用在给学生上课的老师都对teacher通用
开讲座的,讲几节课的讲学和辅导班 用lecturer
instructor是指导老师,只指导不详细的辅导的

teacher 是中小学老师

lecturer 是大学讲师，可以授课的，资深的叫senior lecturer

instructor 是指指导员或者是非授课导师， 国外大学有生活导师， 帮你介绍怎么适应大学生活， 学业导师， 告诉你怎么合理选课， 他们主要是行政人员，没有授课资格。

不可混用的。这里lecturer地位最高， 起码是博士。

teacher
老师, 教师
导师
【航空】教练机
lecturer
讲演者
(大学、学院中的)讲师; 训导者
instructor
教导者; 教师; [美](大学)讲师; 指导员
(研究某学科或问题的)指导书

teacher 层次较为低的老师
lecturer 高水准的
instructor 指导老师