Bond Angle
The angle between two bonds that share a common atom.
Unit
degrees
In depth
Bond angles follow from the arrangement that minimises electron pair repulsion, then shrink wherever lone pairs are present because those repel more strongly. Ring strain, steric bulk and electronegativity of substituents all cause further deviation from the idealised VSEPR values.
Examples in the real world
109.5° in methane, 107° in ammonia, 104.5° in water, and a strained 60° in cyclopropane.