Which term specifically refers to an area of the body between a medial and lateral structure?

Intermediate

Explanation:

Medial structures are located towards the body's median plane, or midline; the midline divides the body from head to toe into left and right halves. Similarly, lateral structures lie on the side of the body, or part away from its middle; arms are lie laterally in relation to the torso which is medial in relation to the body's arms. Areas between these structures are defined as intmmediate.

Example: In relation to the breastbone (medial) and shoulder (lateral), the collarbone is intermediate.  

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