Joy, “io” in Latin reduced to an I with a dot under it that Medieval copyists put at the end of a sentence; a “sign of admiration,” wonderment, emphasis; shortened by computer coders to one syllable, a screamer: bang!
The ancient Greeks, naming it “little star,” used it to mark an error; today, it multiples numbers or marks a footnote, or a less-than-official result, or replaces characters to keep a password secret or offensive words discreet or hold the place of an unknown; or it represents zero or more repetitions, or dereferences a variable in C, whose proponents call it a splat.
It’s a myth that this character’s name derives from “Ampère’s ‘and’”; more likely, it’s a corruption of “and per se,” meaning the character “” by itself is the word meaning “and.” Its glyph is various, but is likely an evolution of the Latin word “et” (meaning “and”) written as a ligature.
Spaces are ubiquitous, separating words thoughts representing time (because you cannot see seconds) and all the things that we don’t know in inner & out in outer spaces filling in in places that nothing fills or is intended to fill.
Originally matching chevrons, sometimes braces or brackets, Desiderius Erasmus called the rounded chevrons lunula crescent blades defending the new moons in their arms containers for whispered thoughts a pair of ears to catch asides showing precedence always from the inside out.
Something in the middle between a pause and a full stop, a semicolon isn’t half of a colon; in English it joins related, balanced, opposed, or contradictory independent clauses; you may use them to separate items in a list that contains commas. Or, when you write, you can avoid them altogether. Many other writers do.
Use a point, full point, or full stop to end a declarative sentence (a point taken) to separate a decimal, that is, to mark the point between the whole and fractional parts of a rational number to separate initial letters to end abbreviations or to delimit parts of a file name, an IP address or URL where it’s called a “dot.”
A grammatical unit smaller than a clause is a komma. A clause is a kōlon. A sentence is a periodos. Obviously, we use a comma to mark a komma, etcetera.