If there is one memory from our childhood related to our education that manages to stay with us through all this years, is the memory of the act of memorizing the spelling from the spelling list and how the teacher would stress that we should all get it right.
Spellings are the basic of any language since without the correct spelling, the meaning of a word might change entirely and just what you might have wanted to communicate in writing to others might be lost to them entirely and they may just end up misunderstanding you or much worse your intentions.
For instance, if you are asking someone to give you six of something and end up saying sex instead, it would not only be an awkward situation for you, but the other party if of the other sex might as well take you to your word and try and make advances.
So it is always necessary to make sure that whatever you are wrting of speaking has the correct pronunciation and the correct spelling.
