The verb sustain means to cause or allow something to continue for a period of time.
Synonyms are assist, bolster, buoy, or preserve.
The word origins from Old French (13th century) sostenir meaning “hold up, bear, suffer, endure”, and from Latin sustinere meaning “hold up, hold upright, furnish with means of support, bear, undergo, endure”. It comes from sub meaning “up from below” plus tenere meaning “to hold”, from PIE root *ten- meaning “to stretch”. The sense of “endure without failing or yielding” is from 14th century.
He has to sustain the needs of his kids.
The economy looks ready to sustain its growth into next year.
We don’t have enough supplies to sustain ourselves on the regular army side.