English translation:
because of, due to, blame
Structure:
Verb + せいで
いAdj + せいで
Noun + の + せいで
なAdj + な/だった + せいで
Explanation:
[cause・unsatisfactory outcome]
Isn’t the grammar description missing the case where せい is followed by だ/です? Apparently, the particle で is not allowed in that case, whereas the grammar summary indicate that it is required there:
✗ ~せいででしょう。
○~せいでしょう。
1 Like
@narfi
Hey 
It is not allowed here, because で in せいで is てform of a noun/なadjective, and the てform is used to connect parts of the sentence (clauses). When せい is used at the end of the sentence (so-called predicate position), there is no other part that will be joined so てform is not needed and as with any other noun/なadjective だ・です・and so on follow.
I will fix the structure section so it will be more clear
Cheers,
I hope it helps!
2 Likes
Hey!
Reading I’ve come upon the “せいか”-grammar!
I tried looking it up and found this grammar structure instead, but it seems like it kinda means the same - maybe せいか being a bit less direct?
Is there a grammar chapter I’ve overlooked or should it even be added here?
Greetings 
Sorry to ping you over something you probably know by now, but I thought it’d be good for people who stumble across your comment.
If you are sure of the reason, use せい
If you are unsure of the reason (but still think it), use せいか