Arabic Grammar: The words which contain vowel markings that can be changed

Title of book: Simplifying Al-Ajrumiyah (English translation of Al-Ajurumiyah)
Title of original book: Matn al-Ajurumiyah fi Ilm al-Nahw (متن الأجرومية في علم النحو)
Author: Abu Abdillah Muhammad bin Muhammad bin Ajurum Al-Shanhaji ( أبو عبد الله محمد بن محمد بن آجروم الصنهاجي)
Born: 1273 CE
Died: 1323 CE, Fes, Morocco
Translator: Abul-Layth Qasim Ibn Aggrey Mutiva
Field of study: Arabic grammar