Complete Selection completes a partially typed function name.

ByteOrdering is an option for BinaryRead, BinaryWrite, and related functions that specifies what ordering of bytes should be assumed for your computer system.

CirclePlus[x, y, ...] displays as x\[CirclePlus]y\[CirclePlus]....

Direction is an option for Limit that specifies the direction in which the limit is taken.

Editable is an option for displayed objects, cells, and notebooks that specifies whether their contents can be edited interactively using the front end.

Identity[expr] gives expr (the identity operation).

Masking is an option for various image analysis and processing functions that specifies on which regions they should operate.

Messages[symbol] gives all the messages assigned to a particular symbol.

Overscript[x, y] is an object that formats as OverscriptBox[x, y].

PrecedenceForm[expr, prec] prints with expr parenthesized as it would be if it contained an operator with precedence prec.