ESEN
Which one to use?Intermediatestructurestructure
So do IvsNeither do I
'So + auxiliary + subject' expresses positive agreement ('me too'); 'neither/nor + auxiliary + subject' expresses negative agreement.
Side-by-side comparison
So do I
structure"So do I" or "So am I" are agreements with affirmative statements: me too. The auxiliary in the response must match the one in the original sentence.
"I love spicy food." "So do I, we should try that new Thai restaurant soon."
"She has already finished the assignment." "So has he, they both worked all weekend."
"I am really enjoying this course." "So am I, the teacher explains things so clearly."
Neither do I
structure"Neither do I" or "Neither am I" are agreements with negative statements: me neither. It works the same way but in the opposite polarity.
"I don't understand why this rule has so many exceptions." "Neither do I, it is confusing."
"She hasn't seen the new exhibition yet." "Neither has he, they plan to go next weekend."
"I didn't enjoy the film at all." "Nor did I. I nearly fell asleep in the second half."
Common mistake
Four common errors:
- 1."So did I work hard" is wrong, the structure is only SO + auxiliary + subject: "So did I."
- 2."So I have" is wrong, inversion is required: "So HAVE I."
- 3."So do I" in response to a negative statement is wrong, use "Neither do I."
- 4."Neither I do" is wrong, inversion is always required: "Neither DO I."
Trick to remember it
Mirror auxiliary rule: the auxiliary in the response must match the original statement. "She is tired" → IS → "So AM I." "They didn't come" → DID → "Neither DID we." Process:
- 1.identify the auxiliary.
- 2.If positive = SO + auxiliary + subject. If negative = NEITHER + auxiliary + subject.
- 3.Auxiliary always goes BEFORE subject.
Quick rule
- •Positive: SO + auxiliary + subject (inversion).
- •"I like it." → "So do I." Negative: NEITHER/NOR + auxiliary + subject (inversion).
- •"I don't like it." → "Neither do I." Colloquial: "Me too" (positive) / "Me neither" (negative).
Did you know?
The structures "so do I" and "neither do I" are examples of what linguists call CLAUSE ELLIPSIS: the omission of predictable parts of the clause to avoid repetition. "I enjoy it, and so does she" instead of "I enjoy it, and she enjoys it too." Ellipsis with inversion is characteristic of English: Spanish uses "yo también" / "yo tampoco" without inversion. English is especially notable for using GRAMMATICAL INVERSION as an agreement-marking mechanism: the position of the auxiliary before the subject signals that this is an agreement response, not an independent declaration. This use of inversion as a pragmatic marker is one of the peculiarities of English that learners take longest to internalize naturally.
Practise what you learned
Exercise 1 · Pick the right one
"I love Italian food." "_____ !" (Agreement)
Exercise 2 · Pick the right one
"I don't like mornings." "_____ . I need three coffees before I can function."
Exercise 3 · Form the word
Related word pairs
EithervsNeither
'Either' refers to one of two (any one); 'neither' refers to neither of the two.
Positive tagvsNegative tag
Question tags are mini-questions at the end of a sentence; a positive statement takes a negative tag and vice versa.
ToovsAlso
'Too' and 'as well' go at the end of the sentence; 'also' goes before the main verb.
AvsAn
'A' is used before consonant sounds; 'an' is used before vowel sounds.
Bryan López
Founder of SpeakUP Academy