An affix is a piece added to a word, or root, which signals or changes its role in a sentence. It is part of grammar.^p18 Affixes may occur in various positions in a word:

• Prefix: before the word/root, for instance: anti-climax; re-write.
• Suffix: after the word/root, for instance: climactic; walked. Most plurals.
• Infix: Inside the word/root. Rare in English, example: the m in recumbent.
• Interfix: between words, to connect them: the reduced and in sun 'n sand; editor-in-chief.