  Whereas Lie had linearized scalar second order ordinary differential
equations (ODEs) by point transformations and later Chern had extended to the
third order by using contact transformation, till recently no work had been
done for higher order or systems of ODEs. Lie had found a unique class defined
by the number of infinitesimal symmetry generators but the more general ODEs
were not so classified. Recently classifications of higher order and systems of
ODEs were provided. In this paper we relate contact symmetries of scalar ODEs
with point symmetries of reduced systems. We define new type of transformations
that build up this relation and obtain equivalence classes of scalar third
order ODEs linearizable via these transformations. Four equivalence classes of
such equations are seen to exist.
