Halochromism is a term that refers to the phenomenon where the color of a substance changes when exposed to different stimuli such as pH levels, temperature or solvent composition. Synonyms for halochromism include chromism, photochromism and thermochromism. Chromism is a broader term that encompasses any change in color, while photochromism occurs when a substance changes color upon exposure to light. Thermochromism refers to a change in color due to temperature difference. Halochromism is often used in the context of chemical analysis and can be observed in indicators and pH meters where color changes are used to indicate the presence of specific substances.