bol

The root bol comes from the Greek verb ballein, "to throw, to cast," and its noun bolē, "a throw." The basic picture is simple and physical: a hand releasing a stone, a spear, a ball into the air. But the Greeks were fond of using "throwing" as a metaphor for almost any act of putting, placing, or directing something — and that is why bol hides inside a strange-looking group of English words that, on the surface, seem to have nothing in common.

The trick is to read each one as "throw + a prefix that tells you which way."

- syn- (together) + ballein → symbol: two things "thrown together" so they match. The ancient Greeks would break a token in half; when two halves were later thrown back together and fit, they proved a bond or identity. A symbol is the half that stands for the whole — a thing that, joined to an idea, fits it perfectly. (Note: sym- here is the assimilated form of syn-, "together," not a separate prefix.)
- pro- (forward, in front) + ballein → problem: something "thrown in front of" you — an obstacle tossed into your path, a question put forward for you to tackle.
- para- (beside, alongside) + ballein → parable and parabola: a thing "thrown beside" another for comparison. A parable sets a story beside a moral truth so you see the likeness. A parabola, in geometry, was a curve laid beside a cone's slope — same word, mathematical sense.
- hyper- (over, beyond) + ballein → hyperbole: throwing beyond the mark. When you exaggerate, you hurl your claim past the truth — "I've told you a million times."
- meta- (change, across) + ballein → metabolism: throwing things into change. Your body constantly "throws" food across into energy and tissue — the ceaseless casting-and-recasting that keeps you alive.
- dia- (across, through) + ballein → diabolic: to "throw across" came to mean to throw accusations at someone — to slander. The Greek diabolos, "slanderer, accuser," became the name of the great Accuser, the Devil. So "devilish" literally traces back to "one who throws charges across at you."

The pattern to hold onto: bol is always a throw. The prefix tells you the direction — together, forward, beside, beyond, into-change, or across — and the modern meaning is just that throw seen as a metaphor.