1. Indicates a cause or reason: “in that, inasmuch as, given.”
Note: Mono de is more polite and formal than no de and kara.
Tōkyō wa bukka ga takai mono de, seikatsu ga taihen desu.
Since prices are high, life in Tokyo is difficult. / Prices in Tokyo being high, it is difficult to make ends meet.
Watashi wa karada ga yowai mono de, nagai ryokō wa muri desu.
In that my constitution is weak [health is poor], long trips are out of the question.