A hyphen, marked thus (-), is employed in connecting compounded words; as, “Lap-dog, tea-pot, pre-existence, self-love, to-morrow, mother-in-law.”
It is also used when a word is divided, and the former part is written. or printed at the end of one line, and the latter part at the beginning of another. In this case, it is placed at the end of the first line, not at the beginning of the second. — Murray.