Bulgarian and Romanian belong to different language families: Bulgarian is a Slavic language whereas Romanian is a Romance language that evolved from Latin.
Despite belonging to different language families, Bulgarian and Romanian have some similar vocabulary words in common. The reason is that Romanian has absorbed some Slavic vocabulary words because of Romania’s proximity to Slavic-speaking countries.
Although a majority of Romanian vocabulary words can be traced back to Latin, there are still a sizable fraction of Romanian vocabulary words which have a Slavic origin. It is estimated that approximately 10% to 20% of Romanian vocabulary words are of Slavic origin.
This is the reason why there are some similar vocabulary words between Bulgarian and Romanian.
Bulgarian and Romanian use different alphabets. Bulgarian uses a Cyrillic alphabet whereas Romanian is written with a Latin alphabet. However, before the mid-19th century, Romanian was written with a Cyrillic alphabet.
Below are some more examples of similar vocabulary words between Bulgarian and Romanian:
The foreign service Institute based on its experience of teaching languages to diplomats has established a classification of languages in terms of their learning difficulty for English speakers.
Romanian is classified as a category 1 language. That is the category of languages that are most similar to English, and hence the easiest for English speakers to learn.
Bulgarian is classified as a category 3 language. That is the category of “hard languages” which present significant linguistic differences compared to English.
Based on this classification, it is estimated to take nearly twice as many hours of study to learn Bulgarian as it does to learn Romanian.
To summarize, Romanian is among the easiest languages for English speakers to learn, whereas Bulgarian is a Slavic language and those are typically ranked among the most difficult languages for English speakers to learn.Conclusion
Bulgaria and Romania are neighboring countries, with Romania located just north of Bulgaria. Despite this geographical proximity, Bulgarian and Romanian are very different languages which are not at all mutually intelligible. Bulgarian is also a much harder language to learn than Romanian.
As a Romance language, Romanian is closer to other Romance languages (such as Italian and French) than it is to Bulgarian. See for instance this comparison of Romanian and Italian.
Because the Romanian language has absorbed some Slavic words into its vocabulary, there are some similar vocabulary words between Romanian and Bulgarian.
For more on the Romanian language, see this list of the 1000 most common Romanian vocabulary words.