A Coordinate (Dative) Bond is a covalent bond in which both electrons come from the same atom.

• Ammonia ($N{H}_3$) has one lone pair of electrons on the nitrogen atom.
• The Hydrogen ion ($H^{+}$) has an empty $1s$ orbital.
• Nitrogen donates its lone pair of electrons to the empty orbital of $H^{+}$.
• Once formed, this bond is indistinguishable from the other 3 normal covalent $N-H$ bonds.