Thayer's Greek Lexicon

 1. a yoke
  1) a yoke that is put on draught cattle
  2) metaph., used of any burden or bondage
1b1. as that of slavery
1b2. of troublesome laws imposed on one, esp. of the Mosaic
law, hence the name is so transferred to the commands of
Christ as to contrast them with the commands of the
Pharisees which were a veritable 'yoke'; yet even Christ's
commands must be submitted to, though easier to be kept
2. a balance, pair of scales