inside, within, between, among, house, home
内 centers on the concept of interiority: being inside, within, or among a bounded space or group. The meanings 'house' and 'home' extend this to the inner domestic sphere.
inside; within
within ...; inside ...
contents; content; substance; matter; detail; import
within the country; inside the county; domestic; home; internal
guidance; leading (the way); showing around
interior; inside; internal
within; inside of; less than
cabinet (of a government); ministry
in the city; within the city
within the (Tokyo) metropolitan area
within the prefecture
inside; interior; inner part
inside a car (train, bus, etc.)
within a company; in-house
interior of the body
secrecy; confidentiality; privacy; secret
internal (e.g. disk); built-in; equipped (with)
inside of a store (restaurant, café, etc.); store interior; on the premises
indoor; inside the room
relatives; one's family
internal organs; viscera
tentative decision; unofficial offer (esp. job offer); informal offer
internal medicine
indoors
内 originally depicted a person entering a dwelling or enclosure, representing the idea of inside. The modern form retains 人 inside 冂, a simplified enclosure.
A person 人 steps inside a framed entrance 冂, so 内 means inside or home.
For ナイ, imagine a person inside their home at night: night -> ナイ, and the person is safely within.