An "activator" is a substance or factor that initiates or speeds up a chemical reaction. In biology, it can refer to a molecule that enhances the activity of an enzyme, making it more effective in catalyzing reactions. Activators play a crucial role in various processes, including metabolism and cellular signaling. In the context of genetics, an activator is a protein that binds to specific DNA sequences, promoting the transcription of nearby genes. This process is essential for regulating gene expression, allowing cells to respond to environmental changes and perform necessary functions. Examples of activators include transcription factors and enhancers.