(english) what structure is this ?

it’s kind of confusing so i’ll try and explain it in the least complicated way. The part of the sentence “always and forever” is added for poetic reasons, to describe HOW little children explain things to adults. It’s what you would call an adverbial clause which is used to define a dependent clause (cannot stand alone as a sentence). As for why “to be” and “explaining” are used is because of it’s tense(I’m not 100% sure but it seems right). Your new sentence does make sense and can be used. sorry if this didn’t help much and you’re welcome if it did 🙂

Well, you can actually say the sentence with or without the “to be'”. They way you said it makes perfect sense as well.

I rememeber learning spanish and, when I did, my instructor said they never use an -ing word (like hablando, escuchando) in the past tense. Like they’d never say they “were eating”… it’s always they HAD eaten or something of that sort.

But we do. I think the “to be” part in front of forever just places a bit more emphasis on the fact that the children are always going to have to be explaining things.

I’m not an english major. I’m sure one could help you a lot more in explaining the breakdown of the setence. =)

Your substitution is perfectly correct, and the sentence makes sense the author’s way and yours.

The construction in question is an adverbial clause explaining what is tiresome.

In this sentence, “explaining” is a present participle and is not a gerund. A gerund is a verb ending in “ing” used as a noun. That is not the case in this example.

Finally, in English, “English” is capitalized.

the use of the gerund (ing form) is to differentiate that each time they explain something its not the same subject that they are explaining ,if you were to use the infinitive form it would imply that the subject was the same and the grown ups were stupid and needed everything explaining to them, so this is why you have to use the gerund