When do I use "that" when is joining two parts of the sentence?

[hmp_khauff]

Q: When do I use "that" when is joining two parts of the sentence?
Example 1: The medecine I took is making me dizzy. (Why isn't it used "that" between the words medecine and I?)
Example 2: The bus that I take every day stops right here. (Why is it used "that" between the words bus and I?)

 

[5jj]

When the relative pronoun 'that' in defining relative clauses is the object of a verb or preposition in that clause, it can be omitted. Both your sentences are fine with or without 'that'.