that

đó, cái đó

used to refer to a person or thing that has already been mentioned or is known about

• that + noun

• I saw a bird. That was a beautiful sight.

  Tôi đã thấy một con chim. Đó là một cảnh đẹp.

rất, quá

used to emphasize how big, good, bad, etc., something is

• that + adj

• That's a huge difference.

  Đó là một sự khác biệt rất lớn.

rằng, để chỉ ra rằng

used to introduce a clause that gives more information about something previously mentioned or known

• that + clause

• I know that you are busy.

  Tôi biết rằng bạn đang bận rộn.

thật sự, thực sự

used to emphasize a statement or opinion, especially when it is surprising or unexpected

• that + adj

• That's really interesting.

  Đó thực sự là điều thú vị.