که

In a sentence

• او گفت که فردا به سفر می‌رود.

  He said that he would travel tomorrow.

  The word 'که' is used as a conjunction to introduce a dependent clause explaining the content of what was said.

• می‌دانم که این کار دشوار است.

  I know that this task is difficult.

  Here, 'که' connects the verb 'می‌دانم' (I know) to the clause providing the information known.

• خوشحالم که موفق شدی.

  I am happy that you succeeded.

  In this sentence, 'که' links the feeling of happiness to the reason for that emotion, forming a coherent expression.