Words grow by attaching smaller pieces. An affix is a bound morpheme that attaches to a root or stem to alter meaning or grammatical function.

Prefixes precede the root, suffixes follow it, infixes sit inside it, and circumfixes wrap around it. English relies heavily on prefixes and suffixes; other languages make richer use of infixes or templatic patterns. Affixes may be derivational, creating new lexical items, or inflectional, marking tense, number, or case.

Recognizing affixes helps readers parse unfamiliar words and supports vocabulary teaching. Historical linguists track how affixes erode, fuse, or arise from once-independent words. The inventory of productive affixes shapes how freely a language can coin new terms.

• Bound morpheme attached to a root or stem
• Includes prefixes, suffixes, infixes, and circumfixes
• May be derivational or inflectional
• Central to word formation and grammatical marking