Shin-Mim-Sin (ش-م-س) has 1 word in the Fahm dictionary: shamsun (sun).
In the Quran, words built on this root occur 33 times in 32 verses, across 28 of the 114 suras. The first is in 2:258. The form شَمْسٌ (sun) accounts for all of them.
And when he saw the sun uprising, he cried: This is my Lord! This is greater! And when it set he exclaimed: O my people! Lo! I am free from all that ye associate (with Him).
He is the Cleaver of the Daybreak, and He hath appointed the night for stillness, and the sun and the moon for reckoning. That is the measuring of the Mighty, the Wise.
He it is Who appointed the sun a splendour and the moon a light, and measured for her stages, that ye might know the number of the years, and the reckoning. Allah created not (all) that save in truth. He detaileth the revelations for people who have knowledge.
Quran 10:5
Arabic text: Tanzil Quran Text (Uthmani 1.1), CC BY 3.0, tanzil.net. English: Marmaduke Pickthall, The Meaning of the Glorious Koran (1930), public domain, via Project Gutenberg. Counts and verse choice: Quranic Arabic Corpus morphology data (corpus.quran.com).