affixation

Affixation is a linguistic process where additional parts, called affixes, are added to a root word to change its meaning or create a new word. These affixes include prefixes (before the root), suffixes (after the root), infixes (inside the root), or circumfixes (around the root). For example, adding "un-" to "happy" forms "unhappy," changing its meaning. Affixation is a common way languages expand their vocabulary and express new or related ideas efficiently.