There are many ways to express understanding and empathy when someone shares their thoughts or feelings with you. Some common synonyms for the phrase "I know what you mean" include "I understand," "I get it," "I hear you," and "I feel you." Each of these phrases conveys empathy and validation towards the person speaking, acknowledging their experiences and showing support. Alternative phrases such as "I can relate," "I empathize with you," and "I've been there too" also express understanding and offer connection and comfort. It's important to acknowledge the feelings and experiences of others, and choosing the right words can make all the difference.