grammar - What's the difference between 意外にも and 意外に?

I was practicing writing for Japanese and I wanted to say, "We don't say it often, but surprisingly, it has the same meaning as "good luck""

My original sentence was "あまり言わないけど、意外に、「がんばって！」と同じ意味だよ。" Several Japanese natives corrected my sentence to:

あまり使わないけど、意外にも/意外なことに、「がんばって！」と同じ意味だよ。

My question is, what's the difference between 意外にも and 意外に？

Thank you in advance.

Answer

意外に works by modifying a single adjective/verb, whereas 意外にも and 意外なことに work by modifying an entire sentence (known as disjunct or sentence adverb in English). Compare the following sentences:

• その本は意外に大きい。
  The book is surprisingly/unexpectedly big.


• 意外にもその本は大きい。
  意外なことにその本は大きい。
  Surprisingly, the book is big.

These are similar, but the former means the size of the book is even bigger than you have expected. The latter means the fact that the book is big is unexpected.

The difference is more critical in the following example:

• 彼は意外にイタリア語ができる。
  He can speak Italian better than you might expect.


• 彼は意外にもイタリア語ができる。
  彼は意外なことにイタリア語ができる。
  Surprisingly, he can speak Italian.

The former is said when you think the listener knows he can speak Italian at least a little. The latter is used when the listener has no prior knowledge about his ability.

Likewise, what you need in your sentence is 意外にも. You are talking about the surprising fact itself, not about the degree of sameness.

Words like 大きい and おいしい can be safely modified by adverbs related to degree such as とても and 意外に, just as you can say "unexpectedly big" or "surprisingly delicious" in English. However, 同じ is unlikely to be modified by adverbs of degree, just as you cannot say "a little same" or "very same" in English. (I may be wrong, but I think "surprisingly same" without a comma is unnatural in English, too.)