In TeXForm#
TeXForm parses this entry as a character leaf mapped to U+03B4 (GREEK SMALL LETTER DELTA).
\bbalpha\bbbeta\bbchi\bbdelta\bbDelta\bbdotlessi\bbdotlessj\bbepsilon\bbeta\bbgamma\bbGamma\bfbbdelta
\bfbbdeltaSymbol
The δ symbol (Greek small letter delta, U+03B4), written as \bfbbdelta in LaTeX math mode.