Congo Red is a synthetic dye that is commonly used in biological research to stain cells and tissues. However, there are several synonyms for the word "Congo Red", which are often used interchangeably. One of the most commonly used synonyms is "Direct Red 28", which is the chemical name for the dye. Other synonyms for Congo Red include "Congo Scarlet", "Cotton Red B", and "Cotton Ponceu 4R". While each of these synonyms refers to the same dye, the different names may derive from variations in the manufacturing process or the intended use of the dye. Regardless of the name used, Congo Red remains an important tool in the study of cellular biology and disease pathology.