What is the difference between "先生(せんせい)" and "教師(きょうし)"

What is the difference between "先生せんせい(せんせい)" and "教師きょうし(きょうし)"

先生せんせい is a title, like Sir, Mr, Mrs 先生せんせい, Dr, etc, and it means Professor, or Pro. It is added to the name:田中たなかさん (Mr. Tanaka);田中先生たなかせんせい。(Pro. Suzuki)

It is the title for teachers and professors of all branches, including masters of martial arts. Being a title, you NEVER use it to refer to yourself.

Just like you never call yourself Sir, or Madame. You cannot call yourself "san", "sama", or "sensei".

On the other hand, 教師きょうし  is teacher or professor. When someone asks you what you do, you say: 教師きょうしです。 You never say 先生せんせいです。

Sample sentences

(1) わたしは 高校教師こうこうきょうしです。
 → I am a high school teacher.

(2) こばやし先生せんせいに 日本語にほんごを ならいます。
  → I will learn Japanese from teacher Kobayashi.