Purpose vs. Purposes

To me they are interchangeable.

For the purpose of. The purpose of this is. I don't think purposes is grammatically correct although I have seen in; in doing this serves the following purposes. Keep the s off the end.

"For the purpose of" is followed by a gerund and can generally be replaced by the word "to" plus the infinitive form of the gerund without changing the meaning.

Example:
The dictionary may be used for the purpose of looking up the definitions of words.
(The dictionary may be used to look up the definitions of words.)

"For the purposes of" is followed

Hi,

I always want to use the phrase "quote unquote", but am getting confused by those whom I always see using it. When should one really use this correctly? Tim

For the licensing purposes or licensing purpose?