Nonstandard describes something that doesn't follow the usual rules, patterns, or expectations for how things are supposed to be done. A nonstandard bolt won't fit the regular wrench size. A nonstandard keyboard might have letters arranged differently than the typical QWERTY layout everyone learns.

In language, nonstandard means words or grammar that differ from what's considered proper or correct in formal situations. Saying “ain't” or “I seen it” is nonstandard English because these forms aren't accepted in formal writing or speech, even though people use them in casual conversation. Standard English follows the rules you learn in school, while nonstandard forms might be perfectly normal in everyday talk but wouldn't appear in a school essay or business letter.

The word often appears in manufacturing and engineering too. Nonstandard parts or measurements can cause problems because things won't fit together properly. Imagine trying to replace a lightbulb if every lamp used a nonstandard socket size: you'd need dozens of different bulb types instead of just a few common ones.

Something nonstandard isn't necessarily wrong or bad. It simply means it doesn't match the agreed-upon way of doing things. Sometimes inventors create better nonstandard solutions that eventually become the new standard.