SIGNIFIERS & SIGNIFIED:

SIGNIFIER = The image in the raw,the physical form - A knife is simply a metal implement
SIGNIFIED = That which carries the meaning, referring to something other than itself - In context of scene involving a murder in a shower this knife signifies death and violence.

Both a Signifier and the Signified join together to make up A SIGN.
Semiotics is able to give account for meanings that are absent as well as present in any given representation.