In [1], the interphase is the intermediate phase between two materials in equlibrium, which will joint to form the composite. The interface is the surface boundary between any homogeneous phases in thermodynamic equilibrium.

[1] Adamson, Physical chemistry of surfaces.

Certainly in monolayers or lipid bilayers, at least, we called interface to the plane separating two phases. While the interphase is a zone which has a given volume, in which are located the polar groups of phospholipid heads, and is an area phenomenologically very different from bulk water or hydrocarbon zone.

Hope this helps in understanding the concept.

Agree with the answers above. In addition 'interphase' used instead of interface is often a typo. Interface meaning the border region between phases is a line of definition between dispersion and solution. The latter term often misused in increasing numbers - particle solution, CNT solution, etc. As long as we have atoms or molecules at the interface in energetically less favourable position than their neighbors in the bulk we have dispersions, when all atoms/molecules are at the interface we have a solution, e.g. micellar solutions, microemulsions.

because of different constitutes are intermixed, there is always a contiguous region.It be simply be an interface .Interface is a some ways analogous to the grain boundaries in monolithic materials and in some cases , however, the contiguouse region is distinct added phase called an inter phase, example, coating on glass fibers in reinforcement plastics .

Interface is the two dimensional BOUNDARY between two surfaces.  Interphase is the three dimensional REGION between two phases.  Thus, we talk of the interfacial adhesion in a fiber-matrix composite being determined by the strength of the interaction between the fiber and the matrix at the interphase. There is an intrinsic problem with this definition that has to do with length scale.  What appears as an interface at large length scales (mm) may look like an interphase at smaller length scales (nm).  I think, it is for this reason, the word interphase is not that widely used in materials science, unless interphase, an intermediate phase, is being explicitly discussed.

I agree with Dr. Murthy.

In a simplistic concept in materials science:

An interface is a sharp two dimensional boundary between two phases. Either or both of these two phases may be solid or liquid or gaseous.

On the contrary, an interphase is the transition zone between two phases in a system i.e. could be solid/liquid, liquid/liquid or liquid/gas. So, can be called an intermediate phase.

interface related to surfaces. Interphase related between two phases

In chemistry physics terms the difference between interface and interphase

is that interface is a thin layer or boundary between different substances or two phases of a single substance while interphase is between phases and is three dimensional region