1. Plaintively.

2. Expressive of sorrow or sadness.

3. Expressing sorrow.

4. Mournful.

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

• plaintifs,
• plaintif,
• plantie,
• plantive,
• plasative,
• olaintive,
• llaintive,
• -laintive,
• 0laintive,
• pkaintive,
• ppaintive,
• poaintive,
• plaintife,
• plaintie,
• pliantive,
• plaintiev,
• pleintive,
• planticel,
• plainwirk,
• Cliantige

• plantain,
• plaintively,
• plaint,
• plaintiff,
• plantagenet,
• plenteously,
• plantal,
• plenty,
• plinth,
• planter,
• pliantness,
• plantlet,
• planty,
• plenteous,
• plantar,
• Plants,
• plantae,
• plant genus,
• planted,
• Plantz,
• pliant,
• plant virus.

The adjective form of the word "plaintive" is "plaintively".

The plural form of the word "plaintive" remains the same, as it does not change in plural form.

The singular form of the word "plaintive" does not exist since "plaintive" is already in singular form. It is an adjective used to describe something that sounds or expresses sadness or sorrow.