Grave, sober, sincere, important, weighty
A synonym for changable is adaptable.
A synonym for common noun is word.
A synonym for debris is garbage. An antonym for debris is cleanliness.
detector or metal detectors
serious or strict
a minor
Serious, critical.
sinceresternsolemnsevere
riotous
Depends on context but 'somber' is one that will fit many situations.
Grave, sober, sincere, important, weighty
ceremony, gravity, sobriety
grave, pressing, serious, severe, extreme, urgent, drastic, daring, furious
no , a synonym is the same meaning for a word and the antonym is the opposite meaning for a word e.g synonym for sad:devastated antonym for sad: happy
There are many synonyms for the adjective "staid". One can interchange the word "staid" with words such as "sedate", "serious", "grave", "steady", and "composed".
Depending on what context: heartbreaking; heartrending; atrocious; flagitious; monstrous; shocking; dangerous; heavy; weighty; serious; severe;