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For a given Lagrangian $L$, the $i$th generalized momentum is defined as $$p_i = \frac{\partial L}{\partial \dot{q_i}}$$ where $\dot{q_i}$ is the time derivative of the $i$th generalized coordinate (i.e. the $i$th generalized velocity).

I have also seen the above referred to as conjugate momenta, or even generalized conjugate momenta. What exactly is the difference between these terms? Do they all mean the same thing?

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There is no difference. Generalized emphasizes the fact that the momenta depend on generalized coordinates (therefore, physical dimensions may be different from $M L T^{-1}$), while conjugate refers to the definition, connected to the Legendre transform underlying the introduction of the $ p$s, starting from the Lagrangian and the generalized coordinates $q$s.

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  • $\begingroup$ +1 Worth adding that it is conjugate to corresponding generalized coordinate. It cannot be conjugate by itself. $\endgroup$
    – Roger V.
    Commented Jan 30, 2023 at 10:04
  • $\begingroup$ @RogerVadim Thanks for the comment. I have added a final part of the last sentence. $\endgroup$ Commented Jan 30, 2023 at 10:36

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