({{, (RefLink[UnderscriptBox, paclet:ref/UnderscriptBox])[x,y]
is the low-level box representation for (Underscript[x, y]) in notebook expressions. }})

OpenersNotesSection(Spacer1)Details and Options

(RefLink[UnderscriptBox, paclet:ref/UnderscriptBox]) is the low-level representation of (RefLink[Underscript, paclet:ref/Underscript]). Except for low-level notebook expression manipulation, (RefLink[UnderscriptBox, paclet:ref/UnderscriptBox]) should not need to be used directly.

Inside \(…\) (RefLink[UnderscriptBox, paclet:ref/UnderscriptBox])[x,y] can be input as x\+y.

In a notebook, an (RefLink[UnderscriptBox, paclet:ref/UnderscriptBox]) can be created using (Key1[ctrl, 4]) or (Key1[ctrl, $]). (Key1[ctrl, space]) moves out of the underscript position.

In (RefLink[StandardForm, paclet:ref/StandardForm]), (RefLink[UnderscriptBox, paclet:ref/UnderscriptBox])[x,y] is interpreted on input as (RefLink[Underscript, paclet:ref/Underscript])[x,y].

(RefLink[UnderscriptBox, paclet:ref/UnderscriptBox])[x,"_"] is interpreted as (RefLink[UnderBar, paclet:ref/UnderBar])[x] or (UnderBar[x]).

The baseline of (RefLink[UnderscriptBox, paclet:ref/UnderscriptBox])[x,y] is taken to be the baseline of x.

(RefLink[UnderscriptBox, paclet:ref/UnderscriptBox])[x,y] is usually output with y in a smaller font than x.

With the option setting (RefLink[LimitsPositioning, paclet:ref/LimitsPositioning])->(RefLink[True, paclet:ref/True]), y is placed in an underscript position when the whole (RefLink[UnderscriptBox, paclet:ref/UnderscriptBox]) is displayed larger, and in a subscript position when it is displayed smaller.

In (RefLink[StandardForm, paclet:ref/StandardForm]), explicit (RefLink[UnderscriptBox, paclet:ref/UnderscriptBox]) objects are output literally. You can use (RefLink[DisplayForm, paclet:ref/DisplayForm]) to see the display form of such objects.

OpenersPrimaryExamplesSection(Spacer1)Examples  (3)

OpenersExampleSection0(Spacer1)Basic Examples  (3)

Display a letter with an underscript:

UnderscriptBox["x","0"]//DisplayForm

An (RefLink[UnderscriptBox, paclet:ref/UnderscriptBox]) form is typically interpreted as an (RefLink[Underscript, paclet:ref/Underscript]) expression:

ToExpression[UnderscriptBox["x","0"],StandardForm]

%//FullForm

The standard formatting for (RefLink[Underscript, paclet:ref/Underscript]) uses (RefLink[UnderscriptBox, paclet:ref/UnderscriptBox]):

ToBoxes[Underscript[x,0],StandardForm]//FullForm

The formatted result looks like this:

Underscript[x,0]

({{DocumentationFooterIconsRelatedFunction.png, ({{See Also}, {(RefLink[Underscript, paclet:ref/Underscript])  ▪  (RefLink[OverscriptBox, paclet:ref/OverscriptBox])  ▪  (RefLink[UnderoverscriptBox, paclet:ref/UnderoverscriptBox])  ▪  (RefLink[SubscriptBox, paclet:ref/SubscriptBox])  ▪  (RefLink[GridBox, paclet:ref/GridBox])  ▪  (RefLink[ScriptSizeMultipliers, paclet:ref/ScriptSizeMultipliers])}})}})

({{DocumentationFooterIconsRelatedTutorial.png, ({{Tutorials}, {▪(RefLinkPlain[Representing Textual Forms by Boxes, paclet:tutorial/RepresentingTextualFormsByBoxes])}, {▪(RefLinkPlain[String Representation of Boxes, paclet:tutorial/StringRepresentationOfBoxes])}, {▪(RefLinkPlain[Typing Underscripts, paclet:tutorial/TypingUnderscripts])}})}})

({{DocumentationFooterIconsRelatedGuide.png, ({{Related Guides}, {▪(RefLinkPlain[Low-Level Notebook Structure, paclet:guide/LowLevelNotebookStructure])}})}})