Q

[1] The letter on the sidewall of a tire denoting the maximum speed for which it is designed (160 kph or 100mph). See speed rating.

[2] A symbol for "throughput."

[3] A symbol for the quantity of water discharged, usually in m³s^-1.

[4] A symbol of merit, often called the Q-factor, for an energy-storing device, resonant system, or tuned circuit.

[5] A symbol for "charge."