preposition, verb, place word, noun, expression, adjective, idiom, measure word · expressing location or time (in, at, on)

他出生于一九九零年。

preposition, verb, idiom, punctuation, noun, expression, pronoun · indicating a target, direction, or relation (to, toward, vis-à-vis, for)

他忠于自己的职守。

verb, preposition, noun, expression, conjunction · used in comparison to indicate degree

质量优于数量。

preposition, adjective, verb · used in the passive voice to introduce the agent

受制于人。

proper name, preposition · literary interjection expressing exclamation or sighing

於！此情此景，真令我感叹万千。

a Chinese surname

於教授是物理学方面的权威专家。