彼の過去については何も知りません。

he; him; his; boyfriend

indicates possessive; nominalizes verbs and adjectives; substitutes for "ga" in subordinate phrases; (at sentence-end, falling tone) indicates a confident conclusion; (at sentence-end) indicates emotional emphasis; (at sentence-end, rising tone) indicates question

the past; bygone days; the previous; a past (i.e. a personal history one would prefer remained secret); one's past; past (tense); preterit; preterite; previous life

concerning; regarding; per (e.g. 100 yen per person); for every

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

what; how many; you-know-what; that; whatsit; what's the expression; what do you call them; what?; hey!

too; also; in addition; as well; (not) either (in a negative sentence); both A and B; A as well as B; neither A nor B (in a negative sentence); even; as much as; as many as; as far as; as long as; no less than; no fewer than; even if; even though; although; in spite of; further; more; again; another; the other

to be aware of; to know; to be conscious of; to cognize; to cognise; to notice; to feel; to understand; to comprehend; to grasp; to remember; to be acquainted with (a procedure); to experience; to go through; to learn; to be acquainted with (a person); to get to know; to concern