"以来" - Chinese dictionary says noun. "Since" in English dictionary says preposition, conjunction. Distinction? A couple of Chinese dictionaries I used says for 以来, part of speech is 名 (noun).

Since in an English dictionary says preposition first.

Is it incorrect to assume a direct correlation between parts of speech between Chinese and English?
There has been an argument for this topic.

In this article, the author stated that "以来" is a "方位词". Which can be seen in reference 5 and 12, it is also refered to as "动态助词".

"方位词" is a type of noun in Chinese, which represents the location (of space / time).

"动态助词" is a type of Chinese particle, you can read it from the link.



Now let's get back to the disagreement. "以来" is defined as a "方位词" in《现代汉语八百词》by 吕叔湘 while is is again defined as a "动态助词" in《现代汉语虚词词典》by 侯学超.

However, "动态助词" also gets its formal definition in《现代汉语八百词》. So if you ask me, I prefer to believe it is a "方位词", which is noun.



As for the different part of speech of the word "since" appearing in English, I guess it is because that "since" is translated as "自……以来", not just "以来". "自……以来" IS a preposition.