Not in the regular, usual, or established form; not according to official, conventional, prescribed, or customary forms or rules; irregular; hence, without ceremony; as, an informal writing, proceeding, or visit.
- Not formal or ceremonious; casual: an informal gathering of friends; a relaxed, informal manner.
- Not being in accord with prescribed regulations or forms; unofficial: an informal agreement.
- Suited for everyday wear or use: informal clothes.
- Being more appropriate for use in the spoken language than in the written language.