Oxford Advanced Learner's Dictionary

[Tingau]

I saw this example (sentence) using despise (v) and under arrest (v/n) from the
Oxford Advanced Learner's Dictionary

1. She despised gossip in any form.
Q: Instead of using despised, why not despises.
She was under arrest on suspicion of murder.
Q: Why not under arrested.

Thank you
Tingau

[Haihao]

She despised gossip in any form. -> She despised gossip in any form in the past; or the event happend in the past.
She despises gossip in any form. -> She despises gossip in any form all the time.

under arrest: preposition + noun = be arrested (correct) .
*under arrested: preposition + participle (incorrect), and redundant in meaning even if to be corrected as: under being arrested.

[Milanya]