Question

sort words according to the meanings of their prefixes or suffixes. sharper easier emptier gloomier semiyearly semimonthly prefix means half or partly suffix means more

Explanation:

The prefix "semi -" means half or partly, so "semiyearly" and "semimonthly" belong to the group with the prefix meaning half or partly. The suffix "-er" often means more in the comparative form of adjectives, so "sharper", "easier", "emptier", "gloomier" belong to the group with the suffix meaning more.

Answer:

Prefix means half or partly: semiyearly, semimonthly
Suffix means more: sharper, easier, emptier, gloomier