The term "be variable" refers to the ability to fluctuate or change over time. The antonyms for this phrase would be "be constant" or "be uniform." These words signify stability and consistency, as opposed to the unpredictable nature of being variable. Being constant suggests a static state or unchanging condition, while being uniform refers to a consistent or standardized quality. These antonyms are often used in the context of scientific experiments, where variables must be controlled and carefully monitored to ensure reliable results. In everyday life, being constant or uniform can also imply dependability, reliability, and steadfastness.