It's important to note that while "истинный" is the most common and formal word, there are other options depending on the context:
* правда (pravda) - can mean "truth" or "true" in a more general sense, especially when referring to something factual or real.
* верный (vernyy) - translates to "true" when referring to something accurate or faithful, like "true to your word."
* подлинный (podlinnyy) - means "authentic" or "genuine" and can be used for something that is truly what it claims to be.
The choice of word depends on the specific situation and the nuance you want to convey.