Element-symbol alternation (all 118 symbols, folded into per-first-letter character classes). Gates formula matching so ordinary prose isn't read as a formula.

The compiled classifier regex (built once).

Companion to GRADE_REGEX for labeled fields ("Grade: Technical"), where an explicit label licenses a bare word-grade stem that would otherwise be too weak to classify. Tried only when GRADE_REGEX finds nothing.

The regex source string — paste into regex101 (ECMAScript flavor) to inspect.