suitable, fitting, relevant, apt, pertinent, befitting, well-suited
allowed, approved, fitting, right, correct, good, suitable, in good condition
Synonyms: convenient, worthwhile, profitable, advantageous, effective, appropriate, beneficial, fit, possible, suitable Antonyms: inexpedient, inappropriate, unprofitable, unbeneficial
A synonym for varied is diverse.
A synonym for temper is temperament.
I don't think there is a synonym for adjoined it is an antonym.
I am searching for an appropriate synonym.
An appropriate synonym for "supplanted" would be "substitute".
appropriate
Trim would be appropriate.
For the purposes of simplicity, I'll presume you're asking for synonyms of laughable. Depending on the situation, 'ridiculous' would generally be an appropriate synonym.
accepted, permitted, official, agreed, appropriate, correct, sanctioned, ratified
co-operativeness
allowed, approved, fitting, right, correct, good, suitable, in good condition
A "decorative cover" would be an appropriate synonym for a duvet cover. While duvet covers are designed to keep dirt away from material, their primary function is decorative.
Depending on the context, appropriate synonyms include demanded, asserted, and took.
The synonym of application may be un-application if that's a word. I am not sure though and I am still looking for an appropriate answer myself.
The antonym of mentor is mentee. Whilst not entymologically correct, the OED has accepted this as an appropriate antonym.