The unit of capacitance

When a battery is connected between the plates of a capacitor, it takes some time before the electric field reaches its full intensity. The voltage builds up at a rate that depends on the capacitance: the greater the capacitance, the slower the rate of change of voltage in the plates.
The unit of capacitance is an expression of the ratio between the amount of current flowing and the rate of voltage change across the plates of a capacitor. A capacitance of one farad, abbreviated F, represents a current flow of one ampere while there is a potential- difference increase or decrease of one volt per second. A capacitance of one farad also results in one volt of potential difference for an electric charge of one coulomb.
The farad is a huge unit of capacitance. You’ll almost never see a capacitor with a value of 1 F. Commonly employed units of capacitance are the microfarad (μF) and the picofarad (pF). A capacitance of 1 μF represents a millionth (10^-6) of a farad, and 1 pF is a millionth of a microfarad, or a trillionth of a farad (10^-12 F).
Some quite large capacitances can be stuffed into physically small components. Conversely, some capacitors with small values take up large volumes. The bulkiness of a capacitor is proportional to the voltage that it can handle, more than it is related to the capacitance. The higher the rated voltage, the bigger, physically, the component will be.