Which term means to leave out something?

The term that means to leave out something is "omit." To omit is to intentionally or unintentionally exclude or disregard certain information, elements, or details when presenting or communicating something, such as in writing or reporting. Understanding the concept of omission is essential, as it emphasizes the importance of what is not mentioned or included in communication.

When considering the other terms, "include" refers to the act of adding or incorporating something rather than leaving it out. "Sustain" typically implies maintaining or supporting something over time, which does not relate to the concept of exclusion. Lastly, "retain" means to hold onto or keep something, in contrast to leaving it out. This distinction clarifies why "omit" is the correct choice.