What is meant by sustain?

In social studies, the word sustain means the ability for a society to survive using a certain practice and resources.

For example, this word is often used when we're discussing energy source.

Experts often argue whether the use of oil as our main source of energy is sustainable for our society. Even though it's cheap, it created a lot of damage to our environment that might be irreversible. They started to point out that it might be the time when people have to start finding other source of energy to sustain their day to day activities (such as solar , wind, or electricity)

she recieved a treatment not thought to be specifically effective in treating her disorder.

answer; not counted as an offense known to the police;