خَاطِئَةٍ

A word in the Arabic language will either be 1) a verb or 2) a noun or 3) a particle – خَاطِئَةٍ is a noun

A noun may either be 1) Definite or indefinite 2) Masculine or feminine 3) Singular, dual or plural 4) Nominative, accusative or genitive

خَاطِئَةٌ is the natural state of this definite noun and it changes to خَاطِئَةٍ due to: 1) a preposition that precedes it or 2) a possessed noun that precedes it or 3) it’s a noun of dependent declension a) نَعْتٌ / صِفَطٌ adjectives b) التَّوْكِيْدُ emphatic c) المَعْطُوْفٌ conjunction d) البَدَلُ synonym

One who makes mistakes

To err, make a mistake, do wrong, commit fault, evil

Surah/Below is the only verse in the holy Quran containing the feminine, active participleخَاطِئَةٍ
Verse
96-16A lying, sinful forelockنَاصِيَةٍ كَاذِبَةٍ خَاطِئَةٍ