Meter (M)
- is the SI unit of length
- it is defined by taking the fixed numerical value of the speed of light in vacuum π to be 299,792,458 when expressed in the unit πΒ·π β1, where the second (π ) is defined in terms of the caesium frequency (Ξπ£πΆπ ). This definition implies the exact relation c = 299,792,458πΒ·π β1