Let W denote the set of words in the English dictionary. Define the relation R by $R=\{(x,y)\in w\times w:$ the words x and y have atleast one letter in common}. Then R is 

R is reflexive because $xRx\forall x.$ R is also symmetric because $xRy\Rightarrow yRx$ 

R is not transitive because for $x=in,y=nose,z=ear$ we find that $xRy$ and $yRz$ but $x\cancel{R}z$ because x and z have no letter common