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A dot above a variable, meaning its derivative with respect to time.
Also known as: Overdot notation, Fluxion notation, Dot over a letter, Newton notation
One dot over a letter is a first derivative with respect to time and two dots is a second. It survives in mechanics because equations of motion are almost always in time, and it is silent about the variable being differentiated with respect to — which is exactly why it is confined to contexts where that variable is never in doubt.
Denotes differentiation with respect to time, one dot per order of derivative.
Contexts: Mathematics
Is Newton's notation, introduced in his fluxional calculus, and is now used almost exclusively in mechanics and dynamics where the independent variable is time by assumption.
Contexts: Mathematics
Does not scale past two or three dots legibly, which is why higher derivatives revert to Leibniz or Lagrange notation.
Contexts: Mathematics
A single small dot centred directly above a letter, or two dots side by side above it.