General parlance is distinct from formal speech or formal writing. It is the variety of language that speakers typically use when they are relaxed and not especially self-conscious. An expression is labeled colloq. for "colloquial" in dictionaries when a different expression is more common in formal speech, but this does not mean that the colloquial expression is inappropriate in formal speech or writing or that it is necessarily slang. Many people misunderstand this very common dictionary label due to the widespread misconception that colloquial means "location" or a word being "regional". This is not the case; the word root for colloquial is related to locution, not location.
Some colloquial speech contains a great deal of slang, but some contains no slang at all. Slang is permitted in colloquial language, but it is not a necessary element. Other examples of colloquial usage in English include contractions or profanity.
In the philosophy of language, "colloquial language" is ordinary natural language, as distinct from specialized forms used in logic or other areas of philosophy. In the field of logical atomism, meaning is evaluated in a different way than with more formal propositions.
A colloquial name or familiar name is a name or term commonly used to identify a person or thing in informal language, in place of another usually more formal or technical name.