Study chinese in china

ten   十[shi] (the second tone) Turn this character 45° either way and you have the X used for the Roman numeral ten.
As a primitive, this character sometimes keeps its meaning of ten and sometimes signifies needle, this latter derived from the character for needle 针. Since the primitive is used in the character itself, there is no need to worry about confusing the two. In fact, we shall be following this procedure regularly.