TEKKI-RI てっきり
Meanings
A situation in which a decision is considered to be almost certain.
This is often used in cases where the results differ from expectations.
Examples
・It was so messy that I thought it had been robbed.
あまりに散らかっていたから、てっきり泥棒が入ったと思った。
・Since you are so talented, I would have thought you had already researched such things.
君は優秀だから、そんなことはてっきりリサーチ済みだと思ったよ。
・I didn’t cook dinner because I thought you were going out to eat, so I thought you wouldn’t be eating at home.
外食してくるって言うから、てっきり家で食事はしないと思って、ご飯作ってないわ。
Dogmatic Opinion
It is used when a prediction made on one’s own is wrong.
Just assumed that was the case, but the results were different.
We haven’t been robbed, he hasn’t done any research, he is saying he wants to have dinner at home.
The person who made the prediction has good reason to expect so.
An expression of a desire to justify the rationale. (I know that’s not what I expected, but I’m not surprised I thought so, am I?)
“Yappari” is to be expected, “Tekkiri” is not what I expected.
Proximate Expression
no doubt
feel sure
quite certain
