Secrecy; something kept confidential or private. A colloquial term often used among friends or family.
それは内緒にしておいてね、まだ公表できないから。
Keep that a secret for now; it can't be announced yet.
子どもにサプライズケーキのことは内緒だよ。
Don't tell the child about the surprise cake.
二人だけの内緒話をしているようだった。
They seemed to be talking about something private just between the two of them.
One's personal circumstances (often financial) that one prefers not to disclose to others.
生活が苦しいが、内緒にしているため誰にも相談していない。
Life is hard, but because it's kept private he hasn't talked to anyone about it.
収入の件は内緒だと言って、家族にだけ話した。
He said the matter of his income was private and only told his family.
In Buddhist usage, inner realization or personal enlightenment — an internal, firsthand conviction or awakening.
禅の修行では、外面的な教えよりも内証が重視されることがある。
In Zen practice, inner realization is sometimes valued more than external teachings.
An archaic usage (written 内所) referring to the kitchen or an inner room of the household; rarely used in modern Japanese.
古い小説には『内所で働く』といった表現が見られることがある。
In old novels you sometimes see expressions like 'working in the inner rooms (kitchen)'.