The book also notes that adding lip rounding to kasrah can make it sound ḍammah-like. Watch especially for unneeded pursing of the lips.
Practice: contrast «سِ» and «سُ». The sound after sīn should remain a short kasrah in the first and a short ḍammah in the second.
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Kasrah drifting toward ḍammah
Correct Vowel Articulation — Fatḥah, Kasrah, Ḍammah, Ishbāʿ and Sukūn
The book also notes that adding lip rounding to kasrah can make it sound ḍammah-like. Watch especially for unneeded pursing of the lips.
Practice: contrast «سِ» and «سُ». The sound after sīn should remain a short kasrah in the first and a short ḍammah in the second.