How do I change the characters used as word delimiters?

Vim uses the characters specified by the ‘iskeyword’ option as word delimiters. The default setting for this option is “@,48-57,_,192-255”. For example, to add ‘:’ as a word delimiter, you can use

    :set iskeyword+=:

To remove ‘_’ as a word delimiter, you can use

    :set iskeyword-=_