Keyword
inside
Info
FrequencyTop 100-200
Type
Kyōiku (2nd grade) 
?
KankenLevel 9
Heisig1095
Readings
ない
(84%)
うち
(14%)
Composed of
upside-down box
person
Mnemonic

A pictograph of a person inside of an upside-down box with only his head sticking out.

Used in kanji (8 in total)
meat
illness
to supply
pattern
third in class
narrowness
archer's left-wrist protector
???
Used in vocabulary (1139 in total)
within ...; inside ...
contents; content; substance; matter; detail; import
guidance; leading (the way); information; notice; announcement (of a visitor's arrival); informing (someone) of a visitor's arrival
Examples (200 in total)
But today, the content doesn't sink into my mind.
Most of the students are probably still in the classroom.
The content can be anything.