Likely, likelier, likeliest. You may also use the Frenchified forms, more likely and most likely. All English adjectives form the comparative in -er. Some snooty people prefer the French form for certain imported or polysyllabic adjectives, thinking that the native English comparatives "sound wrong." But even they must agree that all English adjectives ending in -y take -ier in the comparative.
They don't have single-word forms. They are "More doubtful" and "Most doubtful".
Reliable - more reliable - most reliable
more likely; most likely
its more hopefully and most hopefully
more certain
most certain
likelier
comparative - merrier superlative - merriest
Frequency is a noun and doesn't have a comparative or superlative form.Frequent is an adjective and the comparative form is more frequent and the superlative form is most frequent
comparative=tenser superlative =tensest
The comparative form of tight is "tighter". The superlative form is "tightest".
The comparative form of tinny is tinnier, and the superlative form is tinniest.
More doubtful, most doubtful moister, moistest
comparative - merrier superlative - merriest
"Older" is the comparative form of old. The superlative form is oldest.
more doubtful, most doubtful more wooden, most wooden
Bitter is a comparative and a bittest is superlative
Sweetie is a noun and does not have a comparative or superlative form.
Comparative: older Superlative: oldest
The comparative form of gloomy is gloomier, the superlative form is gloomiest.
The comparative form of cloudy is "cloudier". The superlative form is "cloudiest".
The comparative form of easy is easier, and the superlative form is easiest.
"Easier" is the comparative form of easy. The superlative form is easiest.
"Larger" is the comparative form of large. The superlative form is largest.