How a reaction is written down. Grouped because the notation carries meaning in ways that are easy to miss: an arrow's shape says whether a reaction is reversible, a substance's position above rather than beside the arrow says it is a catalyst, and a double-headed arrow between structures means neither drawing is real. That last one is confused with the equilibrium arrow constantly, and the two assert opposite things.
A single-headed arrow separating reactants from products.
Two half-headed arrows pointing opposite ways, marking a reversible reaction.
A double-headed straight arrow between two drawn structures.
A downward arrow after a formula, marking a solid falling out of solution.
An upward arrow after a formula, marking a gas leaving the reaction.
A formula written above a reaction arrow, naming a catalyst.
Two parallel lines between atoms, representing a shared double bond.
A hexagon with an inscribed circle, representing delocalised aromatic bonding.
A zigzag of lines whose vertices are carbon atoms, with hydrogens left undrawn.
A capital delta before an H, denoting heat absorbed or released.
A flask with a vertical condenser above it, in an apparatus diagram.