Thus, for such concise markings many different types of schemes or solutions are adopted. The value of the capacitor is indicated in “Picofarads”. Some of the marking figures which can be observed are 10n which denotes that the capacitor is of 10nF. In a similar way, 0.51nF is indicated by the marking n51.
This capacitor marking code uses three characters. It bears many similarities to the numeric code system adopted for some surface mount resistors. The first two figures refer to the significant figures of the capacitor value, and the third one acts as a multiplier.
The markings on the capacitors can also be done by printing it on the capacitor. This is true for capacitors which provide enough space for marking to be printed and include film capacitors, disc ceramics, and electrolytic capacitors.
Many larger capacitors like electrolytic capacitors, disc ceramics, and many film capacitors are large enough to have their markings printed on the case. On a larger capacitors there is sufficient space to mark the value, the tolerance, working voltage, and often other data such as the ripple voltage.
The capacitors which are small in size does not provide space required for clear markings and only few figures can be accommodated in the given space in order to mark it and provide a code for their various parameters. Thus, abbreviated markings are used in such cases wherein three characters are used to mark the code of the capacitor.
There could be several reasons why your capacitor terminals are not marked. One possibility is that the markings were accidentally removed or faded over time. Another possibility is that the capacitor is a non-polarized type, meaning it does not have designated positive and negative terminals.