Conjunction: "but"

Explanation:
The sentence "The teacher is strict but kind" contains the conjunction "but."

Conjunctions are words that join words, phrases, or clauses together. They are used to connect ideas and show the relationship between different parts of a sentence. In this case, the conjunction "but" is used to connect two contrasting qualities of the teacher: strictness and kindness.

Conjunctions can be categorized into different types, including coordinating conjunctions, subordinating conjunctions, and correlative conjunctions.

- Coordinating conjunctions join words, phrases, or independent clauses of equal importance. Examples include "and," "but," "or," "so," and "yet."
- Subordinating conjunctions introduce dependent clauses and establish a relationship between the dependent clause and the independent clause. Examples include "because," "although," "while," "since," and "if."
- Correlative conjunctions are pairs of conjunctions that work together to join words or phrases in a parallel structure. Examples include "either...or," "neither...nor," "both...and," and "not only...but also."

In the given sentence, the conjunction "but" is a coordinating conjunction. It is used to connect the two independent clauses "The teacher is strict" and "kind." The word "but" shows a contrast between the strictness and kindness exhibited by the teacher.

Overall, the conjunction "but" is crucial in joining contrasting qualities and ideas within a sentence. Its usage helps to convey a more nuanced and complete meaning.