When referring to the proper meaning, as to the absence of light in space or regarding a color, in Romanian the most common word is the adjective întunecos/-oasă (masc./fem. gender) with the plural întunecoși/-oase.
It comes from the noun întuneric, darkness, ultimately (there is also an adjectival form from the participle întunecat) from the verb a se întuneca, to get dark, to darken. The long infinitive form of the verb is întunecare, with an archaic form înturerecare, from the Latin intenebricare, from tenebrae, darkness. This evolution occurred along with the genesis of the Romanian language.
It can also be used with the figurative meaning as, dangerous, immoral, unenlightened in the context dark mind, minte întunecată, or as gloomy, crestfallen in terms of one’s facial expression, as in a se întuneca la față – one’s face to darken, meaning in Romanian to frown, to scowl.
Interestingly, long after the language genesis, in the XIXth century, Romanian adopted tenebros from French, and now this variant is being used in more formal, erudite contexts overlapping in meaning with întunecat, much like the English tenebrous, although both words have the same Latin root.
A third way of denoting dark can be done by using the adjective obscur, which is identical in both proper and figurative meaning with the English obscure.