residuum

UK: /rɪˈzɪdjʊəm/ US: (ri zij′o̅o̅ əm)

Inflections of 'residuum' (n): npl: residua

WordReference Random House Unabridged Dictionary of American English © 2025

re•sid•u•um  (ri zij′o̅o̅ əm), n., pl. -sid•u•a 

(-zij′o̅o̅ ə). 
1. the residue, remainder, or rest of something.
2. Chemistry Also, residue. a quantity or body of matter remaining after evaporation, combustion, distillation, etc.
3. any residual product.
4. Law the residue of an estate.

• Latin; see residual
• 1665–75

Collins Concise English Dictionary © HarperCollins Publishers::

residuum / rɪˈzɪdjʊəm/ noun ( -ua / -jʊə/)

1. a more formal word for residue