shell - sed whole word search and replace

Question

How do I search and replace whole words using sed?

Doing

sed -i 's/[oldtext]/[newtext]/g' <file> 

will also replace partial matches of [oldtext] which I don't want it to do.

Answer 1

in regular expressions match word boundaries (i.e. the location between the first word character and non-word character):

$ echo "bar embarassment" | sed "s/bar/no bar/g"
no bar embarassment