The verbs diffuse, infuse, and perfuse have a “pour” relationship that is really quite close—etymologically close, that is. Each of these terms has as its basis the Latin word fundere, “to pour,” with only their individual prefixes giving a glimmer of the fine distinctions in their usage. The Latin prefix dis-, “out, apart,” that is a part of diffuse specializes the sense of pouring to that of spreading over a surface, through a space, or in a region: A fluid or gas diffuses throughout a given space at a rate that is usually influenced by the surrounding temperature and pressure. When used as an adjective, diffuse describes something that is spread out or dispersed and has a specific medical usage describing something, such as a disease, that widely affects the body or an organ: The diffuse nature of the cancer ruled out surgery as a means of therapy.
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The verb infuse has the prefix in- as its first component. When a substance is infused, it is introduced, usually by injection, into something else so as to fill or cause filling: A saline solution was infused into the animal’s vein. Chemists also have a specific usage for this verb. It describes the action of steeping or soaking a substance without boiling so as to extract its soluble properties. This activity is not just restricted to chemistry laboratories but is also one that is commonly conducted by many kitchen chemists who pop tea bags into cold water and set the concoction aside, allowing the tea to infuse the water with its flavors and colors.
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In the verb perfuse, meaning “to cause to flow through,” the prefix per- is linked to fundere, thus giving a sense of “thorough, complete, or intense” to the pouring action. As with diffuse and infuse, perfuse has a particular medical usage. It is used to describe the action of artificially supplying an organ, a tissue, or the body with a fluid by circulating that fluid through blood vessels or other natural channels: The organ was perfused with a solution containing a dye in order to determine the rate at which the solution diffused into tissues surrounding the blood vessels.
