Spelling—Identify the correct form of the adjective meaning strict, exacting, or severe (choose among Rigerous, Rigourous, Regerous, Rigorous) with clear rule-based guidance.

Given data

• Meaning: very thorough or strict.
• Options: Rigerous, Rigourous, Regerous, Rigorous

Approach
Standard spelling is rigorous (‘‘ri-gor-ous’’). The variant ‘‘rigourous’’ is nonstandard even in British usage where the noun is ‘‘rigour’’ but the adjective remains ‘‘rigorous’’.

Option analysis
Rigerous/Regerous: vowel errors. ❌Rigourous: incorrect insertion of ‘‘u’’ in the adjective. ❌Rigorous: correct spelling. ✅

Memory tip
Noun: rigor; adjective: rigorous.

Final Answer
Rigorous