SSIM stands for Structural Similarity Index Measure, which is a widely used metric for measuring the similarity between two images. However, there are several synonyms for SSIM. Peak Signal-to-Noise Ratio (PSNR), Mean Structural Similarity Index (MSSIM), Multi-Scale Structural Similarity Index (MS-SSIM), and Universal Quality Index (UQI) are some of them. These metrics measure the similarity of images in a different way and are all used to evaluate the quality of images. The choice of metric depends on the requirement of the user and the purpose of the study. Therefore, understanding the synonyms for SSIM is beneficial for image analysis and research.