v. 1
To keep up; to preserve; to uphold (a state, condition etc.).
It’s important to maintain good posture while sitting.
v. 2
To declare or affirm (a clause) to be true; to assert.
v. 3
To keep in good condition and working order.
v. 4
To keep composed; to keep one's head up; to stay confident, strong, self-assured; to avoid being a victim; to keep oneself from falling apart.
No matter what, you gotta maintain.

Related words

Word family: maintainable
Phrases: maintain appearances

Forms

Past participle: maintained
e.g. maintained → sustained, continued, supported, bolstered…

Choose the right word

Maintain, Keep or Preserve?

In the expressions to keep a secret, keep one's own counsel, keep faith, or keep the faith, such words as preserve or maintain could not be substituted without loss.

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

Example sentences

continue We have to continue doing this until it gets done.
sustain Algeria needs to sustain a better level of growth.
bolster You need some evidence to bolster your claim.
insist I wonder whether or not Tom will insist I do that.
assert Taiwan can't assert its independence from China.

Popularity over time

Word	1850 → 2019	Trend
maintain		steady
continue		steady
sustain		steady
bolster		rising
insist		steady

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

By length

3 letters: say¹
4 letters: back¹, keep¹, hold¹, bear¹, aver²
5 letters: state¹, stand¹, claim¹, carry², adopt², plead¹, exert², wield¹
6 letters: supply², defend², insist², assert², uphold², affirm², allege², upkeep², avouch
7 letters: support², provide², warrant², justify³, observe², declare², sustain², contend², bolster², nourish², espouse², subsist²
8 letters: continue³, champion³, preserve², conserve², propound²
9 letters: entertain³, vindicate³
10 letters: asseverate

The small number after each word is its number of syllables (aver² = 2 syllables).

In other languages

Français: entretenir