What is another word for inner layer?
Pronunciation: [ˈɪnə lˈe͡ɪə] (IPA) 
The term "inner layer" can often be replaced with synonyms such as "interior lining," "innermost stratum," or "deep layer." Other options include "underlying coating," "inward sheet," or "subsurface membrane." These terms point to the layer closest to the core or center of an object, be it a human body part, a geological formation, or a piece of clothing. These synonyms can provide a clearer understanding of the location or function of the inner layer, or simply offer a more versatile vocabulary when discussing the composition and structure of various objects.
