A skeletal formula, also called a line drawing, is a simplified structure in which each line junction, kink or chain end represents a carbon atom. Hydrogen atoms attached to carbon are not drawn but are understood to complete each carbon's four bonds, while multiple bonds and heteroatoms are always shown explicitly. It matters because it lets large molecules be drawn quickly and read clearly. It is the most economical representation, in contrast to the displayed formula, which shows every atom and bond.

骨架式,又称键线式,是一种简化结构,其中每个线条的连接点、折点或链末端都代表一个碳原子。连在碳上的氢不画出,但默认补足每个碳的四根键,而多重键和杂原子则始终明确标出。它的意义在于能快速绘制并清晰读出大分子。它是最经济的表示法,与画出每一个原子和每一根键的展开式形成对照。