This study investigates: what kind of sound change in the lateral sound (sun laam) before the coronal sound of Arabic(/∫/, /ð/, /ð /, /ṣ/, /s/, /d/, /d/, /n/, /ẓ/, /z/, /Ѳ/, /t/, /t /, and /r/).; the extent to which the coronal and the vowel sound cause the elision of the lateral sound and whether the elision of sun laam is the main indicator of geminate the coronal sound. The sample of the study is a list of Arabic words containing the coronal sound of Arabic initially and preceded by a definite article. The significance of this study shows the benefit of describing and analyzing the distinctive features of the immediate sounds within continuant speech for finding out what exactly causes changes in a phoneme in such speech. A descriptive analytic approach is used to describe the distinctive features of the sun laam and the coronal sounds, as well as to analyze the linguistic environment (the sound pattern including the definite article /ال/ /al/ before the coronal sound).The most important results are: the sun laam is completely elided before the coronal sounds. The elision of Sun Laam and the intensity of the vowel sound shape the geminate of the coronal sound.