Part code or value code?
A chip resistor, capacitor or inductor carries its value, not a part number, and writes it with the same few characters a transistor's code uses. The body tells you which way to read them.
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The body decides
A chip resistor, capacitor or inductor is a plain block with a metal cap at each end and no leads. What is printed on it is a value written by a rule, so you decode it rather than look it up.
A body with leads, such as a SOT-23 with three or a SOD-123 with two, holds a semiconductor or an IC, and what is printed on it is a part code its maker chose. The same characters can be either.
One marking, several readings
Each marking below decodes to a value by the rules for resistors, capacitors and inductors, and is printed on parts as a code as well. The values come from the decoders the search uses; the part counts come from our tables.
Reading a resistor code
Three digits are two figures and a multiplier, the number of zeros that follow: 472 is 47 and two zeros, 4.7 kΩ. Four digits work the same way with three figures, on precision parts.
An R is the decimal point: 4R7 is 4.7 Ω, and R47 is 0.47 Ω.
Two digits and a letter are the EIA-96 code of 1 % parts: the digits pick a value from the E96 series and the letter multiplies it, so 01C is 10 kΩ. The two systems can meet: 68R is 68 Ω by the R rule and 4.99 Ω as EIA-96, and nothing in the code says which; the body and the circuit around it decide.
Leaded and MELF resistors carry colour bands instead; the resistor colour code calculator reads them.
Reading a capacitor or inductor code
Most ceramic chip capacitors carry no marking at all, so their value comes from the schematic or from the same position on a working board. Where one is printed, three digits are in picofarads: 104 is 100 nF.
A tantalum capacitor adds a letter for its voltage, and leaded capacitors add tolerance and voltage codes; the capacitor code calculator reads them.
Chip inductors that are marked use the same three digits in microhenries, so 101 is 100 µH, and an R as the decimal point: 4R7 is 4.7 µH.
When you cannot tell
Measure it, lifted from the board. A resistor reads its value on the ohms range. A capacitor reads open, or climbs towards open as it charges. A diode or a transistor reads a junction one way on the diode range and open the other.
If it reads as a semiconductor, the marking is a part code, and How to identify an SMD component takes it from there.
Try it
Search 104: the answer gives the values it reads as, then the parts printed with it as a code.