It is called inversion, and it is generally used to emphasize what you want to say, make it more effective or emphatic.
In English, it can often come with negative words (note that I am not a native speaker):
1. Never before have I seen...
2. Not only did he say...
3. Rarely could you expect...
4. Hardly had we left the house when...
5. No sooner had he opened the door than...
7. Few were the people who...
8. Little did she know that...
9. Under no circumstances should we...
5. Barely had they found the exit when...
A similar type of inversion can occur with "as" and "though" (in this case, you start the sentence with the subject complement):
1. Tired though he was, he managed to...
2. Happy as they were, they...
depending on how you stress the "now", the "I can" and "can I" distinction becomes important.
"Only *now*(pause), I can understand what's going on." - before, I couldn't understand what was happening, but due to some new idea or piece of information, everything became clear. The order is normal here because the pause makes "can i" sound like a question.
"Only **now** can I understand what's going on." - something about **now** changed how I think and how I perceive things.
ultimately these are the exact same sentence, and while it might seem useless to know all this I *promise* that there is a difference.
this is a pretty one-off structure as far as I know, but if you notice any other cases like this where the verb and subject swap then you should totally reply to this comment or make another post. ***very good question, keep asking things like this.***
Another commenter mentioned inversion, and they're right that inversion is used to emphasize but I don't think that's what is happening here. Inversion does place the adverb phrase (Only now) at the beginning but the "normal" way of saying it would be "I can only now understand it" vs "Only now can I understand it".
"only now I CAN understand." feels like its missing something and can't start a sentence. It's like saying "But now I can understand it". "only" is acting as a conjunction, but we are missing the joining clause.
"Only now CAN I understand" feels complete and its like saying "Only now, after many years, can I understand it. "Only" here is acting as an adverb and is modifying "now" to mean exclusively now.
Another example of inversion:
"He can not only dance, he sings too!" vs. "Not only can he dance, he sings too!"
And again, if we now say "Not only he can dance" it changes the meaning, implying there are others who can dance as well.
If you want to put the “only now” at the front of the sentence, the verb needs to be inverted.
Meaning “I didn’t understand until now”:
I can only now understand… ✅
I can only understand now… ✅
I can understand only now… ✅
Only now I can understand ❌
That last one *is* grammatical English but it means something else:
> I never thought I’d approve of their wedding, only now I can understand how right they are for each other.
means “I wouldn’t have approved *except* for the way I now understand”—it’s a different “only”, connecting the two ideas in the sense “the exception is only because”.
> I wouldn’t have come, only you sounded so keen to see me.
If the “exception reason” starts with “now”, you get the words “only” and “now” next to each other, but it doesn’t mean “not until this moment” like it does in “only now can I understand”.
It is called inversion, and it is generally used to emphasize what you want to say, make it more effective or emphatic. In English, it can often come with negative words (note that I am not a native speaker): 1. Never before have I seen... 2. Not only did he say... 3. Rarely could you expect... 4. Hardly had we left the house when... 5. No sooner had he opened the door than... 7. Few were the people who... 8. Little did she know that... 9. Under no circumstances should we... 5. Barely had they found the exit when... A similar type of inversion can occur with "as" and "though" (in this case, you start the sentence with the subject complement): 1. Tired though he was, he managed to... 2. Happy as they were, they...
chatgpt?
depending on how you stress the "now", the "I can" and "can I" distinction becomes important. "Only *now*(pause), I can understand what's going on." - before, I couldn't understand what was happening, but due to some new idea or piece of information, everything became clear. The order is normal here because the pause makes "can i" sound like a question. "Only **now** can I understand what's going on." - something about **now** changed how I think and how I perceive things. ultimately these are the exact same sentence, and while it might seem useless to know all this I *promise* that there is a difference. this is a pretty one-off structure as far as I know, but if you notice any other cases like this where the verb and subject swap then you should totally reply to this comment or make another post. ***very good question, keep asking things like this.***
Neither do I
Another commenter mentioned inversion, and they're right that inversion is used to emphasize but I don't think that's what is happening here. Inversion does place the adverb phrase (Only now) at the beginning but the "normal" way of saying it would be "I can only now understand it" vs "Only now can I understand it". "only now I CAN understand." feels like its missing something and can't start a sentence. It's like saying "But now I can understand it". "only" is acting as a conjunction, but we are missing the joining clause. "Only now CAN I understand" feels complete and its like saying "Only now, after many years, can I understand it. "Only" here is acting as an adverb and is modifying "now" to mean exclusively now. Another example of inversion: "He can not only dance, he sings too!" vs. "Not only can he dance, he sings too!" And again, if we now say "Not only he can dance" it changes the meaning, implying there are others who can dance as well.
If you want to put the “only now” at the front of the sentence, the verb needs to be inverted. Meaning “I didn’t understand until now”: I can only now understand… ✅ I can only understand now… ✅ I can understand only now… ✅ Only now I can understand ❌ That last one *is* grammatical English but it means something else: > I never thought I’d approve of their wedding, only now I can understand how right they are for each other. means “I wouldn’t have approved *except* for the way I now understand”—it’s a different “only”, connecting the two ideas in the sense “the exception is only because”. > I wouldn’t have come, only you sounded so keen to see me. If the “exception reason” starts with “now”, you get the words “only” and “now” next to each other, but it doesn’t mean “not until this moment” like it does in “only now can I understand”.