Teacher
noun, の adjective
A teaching expert/teacher is a teacher.
教師 is a relatively formal word for teachers. Unlike 先生, this word is specifically for people in the teaching profession and cannot be used as a name ender.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
私は法律学の教師をしています。
I work as a teacher of jurisprudence.
あの教師は歴史認識をころころ変えるからあまり好きじゃない。
I don’t like that teacher because he is always flip-flopping on historical facts.
数学教師の机には、理解力をテストする試験の解答が置いてありました。
On the teacher's desk there was an answer sheet for the exam that tests understanding.