Noun and の adjective
きょうし
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.
A teaching expert/teacher is a teacher.
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.