necro - sis
There are many reasons to learn how to divide necrosis into syllables. Separating a word like necrosis into syllables is mainly to make it easier to read and pronounce. The syllable is the smallest sound unit in a word, and the separation of the necrosis into syllables allows speakers to better segment and emphasize each sound unit.
Knowing how to separate necrosis into syllables can be especially useful for those learning to read and write, because it helps them understand and pronounce necrosis more accurately. Furthermore, separating necrosis into syllables can also be useful in teaching grammar and spelling, as it allows students to more easily understand and apply the rules of accentuation and syllable division.
In the case of the word necrosis, we find that when separating into syllables the resulting number of syllables is 2. With this in mind, it's much easier to learn how to pronounce necrosis, as we can focus on perfecting the syllabic pronunciation before trying to pronounce necrosis in full or within a sentence. Likewise, this breakdown of necrosis into syllables makes it easier for us to remember how to write it.