彼が来ることはありえない。

he; him; his; boyfriend

indicates sentence subject (occasionally object); indicates possessive (esp. in literary expressions); but; however; still; and

to come (spatially or temporally); to approach; to arrive; to come back; to do ... and come back; to come to be; to become; to get; to grow; to continue; to come from; to be caused by; to derive from; to come to (i.e. "when it comes to spinach ...")

thing; matter; incident; occurrence; event; something serious; trouble; crisis; circumstances; situation; state of affairs; work; business; affair; after an inflectable word, creates a noun phrase indicating something the speaker does not feel close to; nominalizing suffix; pretending to ...; playing make-believe ...; alias; aka; nickname; alternative name; also known as

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

possible; likely; probable