khorrami wrote:But my question is: "Is it obligatory that we always invert subject-verb order in sentences with "Neither ... nor" at the beginning?
If you're correlating predicates rather than subjects, then you wouldn't place "neither" at the beginning of the sentence at all. You would write:
"He neither
did his homework nor
took a shower."
The examples you gave ("Neither did he do his homework, nor took a shower" and "Neither he did his homework, nor took a shower") are not quite proper English, though the first one is marginally more acceptable than the second one.
Only if you are correlating subjects rather than predicates is it common to place "neither" at the beginning of the sentence. In such cases, you don't invert the subject-verb order:
"Neither
he nor
his pal Jimmy did his homework or took a shower."
CalamityJane wrote:A correlative conjunction must link similar types of words
Your example uses two nouns (homework, shower) but have otherwise
no similarity. A better sentence choice would be:
He neither did his homework nor his other chores.
This sentence isn't quite linking similar types of words either, is it? It's linking "did his homework" (a verb phrase) and "his other chores" (a noun phrase). Seems like the things that follow "neither" and "nor" should be one or the other, but not both. How about:
"He neither
did his homework nor
did his other chores."
or
"He did neither
his homework nor
his other chores."