These are tildes:
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
The tilde was first used in Ancient Greek, and was reintroduced in Mediaeval times as a way of saving parchment. A tilde was put over a vowel normally followed by an n or an m (a tilde is more or less the shape of a stretched n, when you come to think about it) to save having to write in the following letter.
Parchment must have been very expensive.
Nowadays the tilde is used in some languages (eg Spanish, Filipino, Chamorro) to indicate a nasal sound; though in Vietnamese it indicates a dipping tone, and in one version of Ancient Greek it indicated a temporary rise in pitch.
In Japanese email it sometimes acts, rather charmingly, as a sarcasm mark; and in East Asia, even more charmingly, as a sigh.
In music a tilde above a note indicates a twiddle: you play the note written, then the note above it, the first note again, the note below it, then the first note again.
If the tilde is crossed out you do the same thing, only backwards.
Maths treats tildes as twiddles, too: x ~ y is said x twiddle y. It means x and y are nearly equal.
Lastly, and really rather illogically given its use in Maths, in Logic a tilde means not. So ~ p means not p.
Word To Use Today: tilde. This word comes from the Spanish, and before that from the Latin titulus, which means title or superscription (ie, something written along the top).