The word sustain has multiple meanings and can be used in various contexts. Generally, it refers to maintaining or preserving something over time. Here are some common definitions: 1) To keep alive or support the needs of; provide for the ongoing sustenance of someone or something. For example, "We must sustain our planet's resources by using them responsibly." 2) To bear, endure, or tolerate; withstand the impact or pressure of. For instance, "I can't sustain this level of activity for much longer." 3) In music, to play a note or chord that is not sounded continuously but instead is interrupted by other sounds. 4) To maintain a certain condition or state; keep something going over time. An example would be, "We need to find ways to sustain economic growth in our region."