Post-transcriptional gene silencing (PTGS) is the process by which messenger RNA is degraded, preventing the translation of certain genes into proteins. This mechanism is important for regulating gene expression and maintaining cellular homeostasis. There are several synonyms for PTGS, including RNA interference (RNAi), small RNA-mediated gene silencing, and post-transcriptional RNA silencing. Additionally, this process is sometimes called gene silencing by RNA-induced transcriptional silencing complex (RITS) or gene silencing by RNA-dependent DNA methylation (RdDM). While these terms describe different aspects of PTGS, they all refer to the same basic process of regulating gene expression at the post-transcriptional level.