Illustrated Glossary of Organic Chemistry

Bond-line structure (bond-line formula, skeletal structure, skeletal formula): A representation of molecular structure in which covalent bonds are represented with one line for each level of bond order. A single bond is represented with a single line, a double bond is shown by two parallel lines, and a triple bond by three parallel lines. The position of carbon atoms may be shown with letters, or may be implied (in certain circumstances). Similar, but not identical to, Lewis structure.

Bond-line structural representation of Taxol (paclitaxel), an anticancer drug.