Semiotics

The study of signs and symbols. Sheldon needed help in this area to interpret the meaning of a necktie hanging on Leonard's doorknob.

Sheldon: I need your help in a matter of semiotics.

Penny: What?

Sheldon: Semiotics, the study of signs and symbols as a branch of the philosophy related to linguistics.

Penny: Okay, sweetie, I know you think you are explaining yourself, but you're really not.