noun
nightie
NY-tee/ˈnaɪti/
A loose garment worn by a woman or girl for sleeping.
The loose cotton nightie hangs from a wooden hanger.

Etymology
Nightgown names a loose gown put on at night. Nightie began as a children’s shortening of that name and denotes the sleeping garment.
More examples
- Her daughter picks a nightie with little stars on it.
- I pack two nighties for the weekend trip.
- She slips a robe over her nightie before answering the door.
Forms
nightie · nighties
Similar words
- nightgown
- A more neutral term for the same sleeping garment.
- nightshirt
- Resembles a long shirt and is worn by either sex.