Covalent Bond
Definition
A bond where atoms share electrons instead of trading them. It is the bond holding water, DNA, and plastics together.
Technical definition
A covalent bond forms when two atoms share one or more pairs of electrons, typically between nonmetals with similar electronegativities. Shared pairs count toward both atoms' octets, and bonds may be single, double, or triple.
Example
In methane (CH4), carbon shares one electron pair with each of four hydrogen atoms: four single covalent bonds.
Common confusion
Sharing does not have to be equal. In a polar covalent bond like H-Cl, the electrons spend more time near chlorine, giving the bond partial ionic character.