Answer:
sleep terror; nightmare
Explanation:
Even though they have strong similarities (Dreams that are perceive as 'scary' or uncomfortable) there are some distinct differences between the two.
- Nightmare occurs during REM while sleep terror occurs between cycles.
- Between the two, sleep terror tend to be accompanied by physical response such as screaming or other violent movements.
- Nightmare tend to be remembered by the receiver for a long period of time, while sleep terror tend to be dissapear from the receiver's recollection when they woke up.