external vs on the surface

external

adj
  • Relating to or denoting a medicine or similar substance for use on the outside of the body. 

  • Having existence independent of the mind. 

  • Situated near or toward the surface of the body. 

  • For or concerning students registered with and taking the examinations of a university but not resident there. 

  • Not contained in the main computer. 

  • Outside of something; on the exterior. 

  • Not intrinsic or essential. 

  • Provided by something or someone outside of the entity (object, group, company etc.) considered. 

  • Using a disk or tape drive rather than the main memory. 

  • Relating to or connected with foreign nations or institutions. 

  • Having merely the outward appearance of something. 

noun
  • Outward appearance. 

  • Inessential or superficial features. 

  • A variable that is defined in the source code but whose value comes from some external source. 

  • The exterior; outward features or appearances. 

on the surface

prep
  • apparently, outwardly; superficially 

How often have the words external and on the surface occurred in a corpus of books? (source: Google Ngram Viewer )