LinkClose[link] closes an open MathLink connection.

LocalizeVariables is an option to Manipulate that determines whether the values of variables associated with controls should be localized.

LocatorRegion is an option for Locator that specifies where the locator object should by default be allowed to go when it is dragged.

MatchLocalNames is an option for Trace and related functions that specifies whether symbols such as x should match symbols with local names of the form x$nnn.

MatchQ[expr, form] returns True if the pattern form matches expr, and returns False otherwise.

None is a setting used for certain options.

NullRecords is an option for Read and related functions which specifies whether null records should be taken to exist between repeated record separators.

NumberPoint is an option for NumberForm and related functions which gives the string to use as a decimal point.

OutputStream["name", n] is an object that represents an output stream for functions such as Write.

PageFooters is an option for notebooks that specifies what should be inserted as the footer of each page of a notebook when it is printed.