couple vs pair

couple

verb
  • To cause (two animals) to copulate, to bring (two animals) together for mating. 

  • To join in sexual intercourse; to copulate. 

  • To join (two things) together, or (one thing) to (another). 

noun
  • A small number. 

  • That which joins or links two things together; a bond or tie; a coupler. 

  • A couple-close. 

  • Two partners in a romantic or sexual relationship. 

  • One of the pairs of plates of two metals which compose a voltaic battery, called a voltaic couple or galvanic couple. 

  • Two of the same kind connected or considered together. 

  • A turning effect created by forces that sum to zero in magnitude but produce a non-zero external torque. 

adj
  • Two or (a) small number of. 

det
  • Two or a few, a small number of. 

pair

verb
  • To bring two (animals, notably dogs) together for mating. 

  • To engage (oneself) with another of opposite opinions not to vote on a particular question or class of questions. 

  • To group into one or more sets of two. 

  • To suit; to fit, as a counterpart. 

  • To come together for mating. 

  • to link two electronic devices wirelessly together, especially through a protocol such as Bluetooth 

noun
  • A couple of working animals attached to work together, as by a yoke. 

  • A boat for two sweep rowers. 

  • A score of zero runs (a duck) in both innings of a two-innings match. 

  • Used with binary nouns (often in the plural to indicate multiple instances, since such nouns are plural only, except in some technical contexts) 

  • A double play, two outs recorded in one play. 

  • The exclusion of one member of a parliamentary party from a vote, if a member of the other party is absent for important personal reasons. 

  • Two similar or identical things taken together; often followed by of. 

  • Two members of opposite parties or opinion, as in a parliamentary body, who mutually agree not to vote on a given question, or on issues of a party nature during a specified time. 

  • In a mechanism, two elements, or bodies, which are so applied to each other as to mutually constrain relative motion; named in accordance with the motion it permits, as in turning pair, sliding pair, twisting pair. 

  • One of the constituent items that make up a pair. 

  • A doubleheader, two games played on the same day between the same teams 

  • A poker hand that contains two cards of identical rank, which cannot also count as a better hand. 

  • A pair of breasts 

  • A pair of testicles 

  • Two people in a relationship, partnership or friendship. 

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