When a word is prefixed with the definite article, the first consonant of the word is emphasized with a דּגֵשׁ (DDaGeSh). While the definite article receives a פַּתָּח (PPaTTaX).
However, the following consonants are unable to receive a דּגֵשׁ
The vowelisation of the definite article is further modified to receive a סֶגוֹל (segol) הֶ instead, if the first consonant of the word is either
Exception to Rule 3.
If the first consonant is pronounced with an accent, the definite article reverts to receiving a פַּתָּח as its vowelisation.