1. At that place; on that account.

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

• theret,
• thereoy,
• threst,
• threath,
• threaty,
• theray,
• thereapy,
• therad,
• therei,
• theeast,
• therapt,
• theran,
• thrroat,
• therepay,
• theree,
• therap,
• thert,
• threast,
• thearea,
• therats

The adjective form of "thereat" is "thereatening".

The plural form of "thereat" is "thereats".

The singular form of the word "thereat" is "thereat". It is an adverb and does not change form for singular or plural usage.