"I can definitely understand" is correct and usable in written English. You can use this phrase to express agreement or comprehension with something that someone has said or written. For example, "I understand why you're feeling so frustrated - I can definitely understand."
But this I can definitely understand".
"You hate to stereotype, but I can definitely understand why they were afraid".
"So I can definitely understand how he might be feeling about what may come out of some of the people.
After today, I can definitely understand why French farmers would choose to follow an agro-tourism path and focus on niche production of quality versus commodity production of quantity.
I can definitely understand why should would say that.
"And I can definitely understand where they're coming from". Does that mean you should forgo the added protection and take your chances?
Rosie, a 17-year-old heterosexual female from Chicago, Illinois, also pointed out that Snapchat is used as a safety and legitimacy filter: "You can definitely understand if a guy is a creep over Snapchat, though, and see what they actually look like, which is good for both parties".
We can definitely understand how North would be a little freaked out, though we have a feeling the she'll come around to it eventually.
Listen, we can definitely understand having that one friend that ropes you into their hairebrained scheme to make some extra money.
I can definitely see the upside.
I can definitely see why.
Being a terminologist, I care about word choice. Ludwig simply helps me pick the best words for any translation. Five stars!
Maria Pia Montoro
Terminologist and Q/A Analyst @ Translation Centre for the Bodies of the European Union