Note  in  the  following  paragraph  how  the  word  courteous^  the  key
word  in  the  topic  sentence,  is  expanded  and  repeated  in  the  sentences
that  follow,  by  such  words  and  phrases  as  are  written  in  italics:

He  was  the  most  courteous  salesman  I  had  ever  seen.  He  was  born  polite.  His
easy  hearing  and  gracious  manner  were  not  planned  or  studied ;  they  were  there  and
just  could  not  help  coming  out.  He  made  me  feel  that  he  took  a  genuine  pleasure
in  showing  me  the  merchandise.  I  changed  my  mind  a  thousand  times;  yet  he
remained  pleasant  and  smiling  through  it  all.  He  answered  all  my  questions  kindly
and  never  interrupted  me  while  I  was  speaking.  Inasmuch  as  I  have  the  habit  of
talking  continuously,  I  consider  this  his  greatest  feat  in  manners.  When,  after  a
half  hour  or  so,  I  said,  "I  believe  I  shall  not  take  it  today,"  he  replied,  ^' Sorry,
Madam;  some  other  time  perhaps."  When  he  handed  me  my  umbrella  and  a  small
parcel  I  had  placed  on  the  counter  and  forgotten,  I  confess  I  was  overwhelmed,  and
— well,  I  just  reconsidered  then  and  there,  and  changed  my  mind.  I  bought  the
goods!  His  courtesy,  always  just  right — never  failing,  never  overdone — had  sold
me  completely.
The  paragraph  has  unity.  Every  idea  in  it  is  centered  in  the
word  courtesy  in  the  topic  sentence,  and  the  word  itself  is  reflected
or  echoed  by  certain  words  and  phrases  in  the  succeeding  sentences.
