covering vs focus

covering

noun
  • That which covers or conceals; a cover; something spread or laid over or wrapped about another. 

  • Action of the verb to cover. 

  • A continuous map onto a topological space X, 𝜋:E→X, such that there exists a discrete space D and for every x∈X an open neighborhood U⊂X, such that 𝜋⁻¹(U)= displaystyle bigsqcup _(d∈D)V_d and 𝜋|_(V_d):V_d→U is a homeomorphism for every d∈D. 

focus

verb
  • To adjust (a lens, an optical instrument) in order to position an image with respect to the focal plane. 

  • To transfer the input focus to (a visual element), so that it receives subsequent input. 

  • To direct attention, effort, or energy to a particular audience or task. 

  • To concentrate one’s attention. 

  • To concentrate during a task. 

  • To cause (rays of light, etc) to converge at a single point. 

  • To aggregate figures of accounts. 

noun
  • The fact of the convergence of light on the photographic medium. 

  • A point of a conic at which rays reflected from a curve or surface converge. 

  • The most important word or phrase in a sentence or passage, or the one that imparts information. 

  • The quality of the convergence of light on the photographic medium. 

  • A point at which reflected or refracted rays of light converge. 

  • The exact point of where an earthquake occurs, in three dimensions (underneath the epicentre). 

  • The status of being the currently active element in a user interface, often indicated by a visual highlight. 

  • Concentration of attention. 

  • An object used in casting a magic spell. 

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