彼は怪我がもとで死んだ。

he; him; his; boyfriend

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

injury (to animate object); hurt

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

origin; source; base; basis; foundation; root; cause; ingredient; material; (somebody's) side; (somebody's) location; original cost (or capital, principal, etc.); (plant) root; (tree) trunk; first section of a waka; counter for blades of grass, tree trunks, etc., and for falcons (in falconry); handle (chopsticks, brush, etc.); grip

indicates location of action; at; in; indicates time of action; indicates means of action; cause of effect; by; and then; so; indicates continuing action; indicates certainty, emphasis, etc.

to die; to pass away; to lose spirit; to lose vigor; to look dead; to cease; to stop