Browsing Brazilian Portuguese translation

Translators: This phrase is spoken to inform the user that what is about to
be spoken is underscripted text in a mathematical expression. Note that the
underscript might be simple text or may itself be a mathematical expression,
and in this instance we have no additional context through which a more user-
friendly word or phrase can reliably be chosen. Examples of underscripts:
http://www.w3.org/TR/MathML/chapter3.html#presm.munder
https://reference.wolfram.com/language/ref/Underscript.html