Dadra is a light classical style which is very similar to thumri.  Although it resembles thumri it is much looser and allows more freedom for the artist.  The tals used are dadra of 6 beats, kaherava of 8 beats, or any other light tal.  It is commonly performed in light rags such as mand, pilu or pahadi. 'thumri' usually portrays various moods of love whereas, a dadra is slower in tempo and does not have very elaborate wordings. 'dadra' talks more of nature and seasons.