What does it mean when a substance is described as hydrophilic?

When a substance is described as hydrophilic, it means that it has a high affinity for water molecules. This characteristic allows hydrophilic substances to interact favorably with water, leading to their ability to dissolve in it or form favorable interactions with it, such as through hydrogen bonding. Hydrophilic molecules, often polar or charged, tend to mix well with water, which is a polar solvent, thus facilitating various biological processes, such as nutrient absorption and cell signaling. This property is crucial in many biological contexts, such as the formation of cellular membranes and the transport of substances in biological systems.