Quick question about some so-called "adverbs". I've seen some people claim that noun + に particle (本当に) isn't really an adverb. If it isn't an adverb, then does anyone know what the function of the に particle is here?

I've seen monolingual dictionaries say that these are adverbs, but then there are people claiming that they are only called adverbs in textbooks to simplify things for English speakers. Both seem plausible - which is true?

  • 1
    Is your question specifically about 本当に?
    – user1478
    Commented Dec 14, 2013 at 22:24
  • 1
    Nope. More about the function of に after nouns (like 本当)
    – user4096
    Commented Dec 15, 2013 at 8:55
  • Like...実際に、即座に、とっさに, maybe? (We don't say 本当な、実際な、即座な、とっさな but 本当の、実際の、即座の、とっさの)
    – user1016
    Commented Dec 19, 2013 at 15:22
  • What about 元気? At least what I learned is that 元気な and 元気の are both possibly used by native speakers as is 元気に.
    – virmaior
    Commented Dec 20, 2013 at 7:29

2 Answers 2


If you wish to know what part of speech 本当に is according to "school grammar" in Japan, then it is a [副詞]{ふくし}. Every kid in Japan is being taught that it is a 副詞 as I type this. I want to stress that using English grammar terms such as "adverb" and "adjective" will only slow down your Japanese study in the long run, trust me.

There are a handful of people who claim otherwise regarding 本当に, I admit. So the choice is yours. You could either join the main school of thought or go independent. After all, words never come with tags telling what parts of speech they belong to. You will need to decide which theory makes more sense or seems more persuasive.

I learned English in Japan by using whatever books that happened to be around me (and there were only a few). Years later, do I look like I know nothing about English grammar? Do you have difficulty in reading my English?

You will surely need to know what types of words 本当に can modify in order to use it correctly, but whether you believe the word is a 副詞 or not will not make a cool topic at the party. Cheers!


Well it certainly functions the same as an adverb. Just as in English, it tell the extent or how much of something.

  • 3
    That definition doesn't work for English adverbs, either--consider adverbs like also or wrong, for example. No semantic definition will work for any part of speech, I'm afraid.
    – user1478
    Commented Dec 15, 2013 at 4:44
  • Of course that's a definition of an adverb. It doesn't represent ALL the definitions. Adverbs are probably the most complex part of speech because adverbs can modify verbs, adjectives and other adverbs. In this case "honto" represents the adjective "true" while "hontoni" represents the adverb "truly."
    – 泣き虫
    Commented Dec 16, 2013 at 2:32
  • @泣き虫 本当 is not a Japanese adjective. Per dictionary.goo.ne.jp/leaf/jn2/206289/m0u/%E6%9C%AC%E5%BD%93, it is 名詞・形用動詞. Putting な after it makes it function adjectivally. に makes it function adverbally... Japanese for foreigners teaches these 名詞/ナ形容詞 but Japanese people don't use the latter term. Adverbs are definitely the most complex part of English speech; not sure if that's true of Japanese.
    – virmaior
    Commented Dec 19, 2013 at 13:32
  • でも「本当な」って言わないんですよね・・・「本当に」は、ちょっと難しいみたいです。home.alc.co.jp/db/owa/jpn_npa?sn=73
    – user1016
    Commented Dec 19, 2013 at 15:01
  • Thank you for agreeing with me that 本当に is an adverb. The questions of 本当な was only brought up by you.
    – 泣き虫
    Commented Dec 22, 2013 at 18:24

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