What term describes the line that forms between two immiscible liquids?

The term that describes the line that forms between two immiscible liquids is "interface." This term is used in various scientific disciplines, including chemistry and physics, to refer to the surface or boundary where two different phases meet but do not mix. For instance, when oil and water are poured together, they do not mix due to their differing polarities, and the line at which these two liquids come into contact is referred to as the interface. The properties of the interface are often key in understanding phenomena such as surface tension and emulsification.

The other terms do not accurately capture the specific concept in this context. A "boundary" generally refers to any dividing line or separation, but it is not as specific as "interface," which particularly pertains to the interaction between two distinct phases. "Seam" usually denotes a line where two pieces are sewn together, which does not apply in the context of liquids. "Division" typically signifies a separation or split but lacks the specificity necessary for describing the physical properties and interactions at the meeting point of the two immiscible liquids.