This document discusses various ways to ground the symbols used in knowledge graphs. It describes the traditional "symbol grounding problem" where symbols are defined based only on other symbols. It then outlines several approaches to grounding symbols in non-symbolic ways, such as by linking them to perceptual modalities like images, audio, and simulation. It also discusses grounding symbols via embeddings, relationships to physical entities, and operational semantics. The document argues that richer grounding could help integrate these notions and enhance interoperability, exchange, identity, and reasoning over knowledge graphs.