酸化: oxidize, become oxidized / 参加: participate, join, take part

A title used after person's name (first name or surname) regardless of sex; Mr, Ms, Mrs, Miss. Also used after a job title and a company name. / (colloquial) Used after a shop name.

三人: three people

三角形: triangle

三月, 3月: March

賛意: assent / 三位: third rank / 三尉: second lieutenant

紋章学: heraldry

Synonym of たまらない (tamaranai)

門下生: disciple

(idiomatic) it's no big deal, it's not the end of the world (if you do it)