What do we call substances that are repelled by water?

Substances that are repelled by water are referred to as hydrophobic. The term "hydrophobic" comes from the Greek words "hydro," meaning water, and "phobos," meaning fear. Thus, hydrophobic substances do not interact well with water molecules and often prefer to remain separate. This characteristic is crucial in various biological processes, including the formation of cell membranes, where hydrophobic and hydrophilic properties help create a phospholipid bilayer that serves as a barrier to most water-soluble substances.

In contrast, substances that are attracted to water are classified as hydrophilic, which allows them to dissolve or interact favorably with water. "Hypotonic" describes a solution with a lower solute concentration compared to another, affecting the movement of water across cell membranes, while "hypha" refers to a filamentous structure found in fungi, unrelated to water interactions. Understanding these distinctions aids in comprehending cellular structures and biological interactions.