A house is hidden by foliage; the bird's nest is artfully concealed. Whatever is buried is hidden or concealed; but there are many ways of hiding or concealing a thing without burying it.

J. C. Fernald, English Synonyms and Antonyms (1914)

Example sentences

secret Tom happened to let out the secret to his friends.
hidden She has to keep her powers hidden from her family.
covert We have been sent on a covert mission.
silent As he didn't know what to say, he remained silent.

Popularity over time

Word	1850 → 2019	Trend
concealed		steady
secret		rising
hidden		rising
covert		rising
silent		rising

Use in printed books, per decade from 1850 to 2019.

By length

4 letters: dark¹, snug¹
5 letters: close¹
6 letters: secret², hidden², silent², unseen², covert², sneaky², latent², occult², veiled¹
7 letters: obscure², furtive²
8 letters: stealthy²
9 letters: invisible⁴, incognito⁴, recondite³, unseeable
10 letters: mysterious⁴, undercover⁴, obfuscated
11 letters: clandestine³
13 letters: surreptitious⁴

The small number after each word is its number of syllables (secret² = 2 syllables).

In other languages

Français: dissimulé
Italiano: dissimulato