suffix

An affix added to the end of a word or stem, serving to form a new word or functioning as an inflectional ending, such as -ness in gentleness, -ing in walking, or -s in sits.

To add as a suffix.

To attach at the end: specifically used of adding or annexing a letter or syllable, a suffix.

In. grammar, a letter or syllable added or annexed to the end of a word or to a verbal root or stem; a formative element, consisting of one or more letters, added to a primitive word to make a derivative; a postfix; a terminal formative, as the -th of length, the -d of loved, the -ly of godly, the -ly of badly, etc.

In mathematics, an index written after and under a letter, as x0, x1, x2, x3.