A nightgown, nightdress or nightie, is something you wear to sleep in. Only girls and women wear nighties.
A nightmare is a bad dream. Nightmares can be extremely frightening, and make you wake up scared.
You might also use nightmare to describe a particularly bad event, for example "we had a nightmare vacation".
There are nine sunglasses in the picture. The number before nine is eight. The number that comes after nine is ten>.