GapPenalty is an option for SequenceAlignment and related functions that gives the additional cost associated with each gap corresponding to a run of insertions or deletions.
GenerateConditions is an option for Integrate, Sum, and similar functions that specifies whether explicit conditions on parameters should be generated in the result.
Inner
(Built-in Mathematica Symbol) Inner[f, list_1, list_2, g] is a generalization of Dot in which f plays the role of multiplication and g of addition.
InputStream["name", n] is an object that represents an input stream for functions such as Read and Find.
Masking
(Built-in Mathematica Symbol) Masking is an option for various image analysis and processing functions that specifies on which regions they should operate.
MaxPlotPoints is an option for plotting functions like ArrayPlot and ListPlot3D that specifies the maximum number of points that will explicitly be included in the output.
NumberMultiplier is an option for NumberForm and related functions which gives the string to use as a multiplication sign in scientific notation.
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.
ReadProtected is an attribute that prevents values associated with a symbol from being seen.