a person whose occupation is teaching
"The new teacher arrived early to set up her classroom for tomorrow's lesson."
a personified abstraction that teaches
"books were his teachers"
"experience is a demanding teacher"
A person who teaches, especially one employed in a school.
"The new teacher arrived at the elementary school today to begin her first class."
In plain English: A teacher is someone who helps you learn new things at school.
"My teacher helped me understand the difficult math problem."
Usage: Use teacher to refer specifically to an educator working within a formal school setting rather than someone giving informal lessons or training animals. This term is distinct from synonyms like instructor or tutor when the primary role involves teaching students at a recognized educational institution.
The word teacher comes from Middle English and was formed by adding the suffix "-er" to the verb teach. It entered English with the straightforward meaning of someone who teaches, reflecting its original function without significant shifts in definition over time.