When do you add most in front of an adjective?

Answer 1

Most is used before an adjective to form a superlative. Most is only used when the comparative can't be formed normally with "-est" (as in fastest, brownest, happiest, etc.) or an irregular (best for good, worst for bad, least for little, etc.). For any given word, you just have to know (or look up) whether "-est" or "most" is used; but words with three or more syllables tend to use "most", as in "most annoying" (not "annoyingest"), "most suspicious" (not "suspiciousest"), "most practical" (not "practicalest"), "most persistent" (not "persistentest"). This is not always true, however: unhealthiest and most unhealthy are both correct, as are almightiest and most almighty. Sometimes it changes over time: People used to say sublimest, but now most sublime is much more common; most stupid has been entirely replaced by stupidest. Funnest is famously unaccepted (in favor of more fun), but it is nonetheless in wide use.