1. To.

Nuttall's Standard dictionary of the English language By Nuttall, P.Austin

• intob,
• inbto,
• unfor,
• inito,
• ninto,
• untii,
• inton,
• unitof,
• aunti,
• untra,
• intop,
• untl,
• inyo,
• usato,
• tnto,
• omnto,
• unle,
• unioq,
• into,
• uncc

• unity,
• unit,
• uniat,
• undo,
• unite.

The plural form of "unto" is "untos". However, it is worth noting that "unto" is not commonly used in modern English and is considered archaic.

The singular form of the word "Unto" is "Unto". "Unto" is already the singular form of the word, as it does not change for plural or singular.