Reply to the Comment of X. Ji on "Do gluons carry half of the nucleon momentum?" [PRL 103:062001 (2009)]

We affirm that the proper momentum defined in [PRL 103:062001 (2009)] does respect exact gauge symmetry and is as measurable as the kinetic momentum. The physical part of the gauge field is also as measurable as the electromagnetic field. The Comment of Ji [arXiv:0910.5022] is due to a misunderstanding of our work, and a typical confusion of our gauge-invariant formalism with the specific Coulomb-gauge calculation.