1. With too and so respectively
Differences between Either and too (both either and too are used at the end of a sentence) –
Consider this example –
Person 1 – I got good marks.
Person 2 – I got good marks too.
We use either as a negative –
Person 1 – I did not get good marks.
Person 2 – I did not get good marks either.
In the above sentences, we will be tempted to use too which is incorrect. “Too” has to be used with a positive verb. Here is another example to reinforce this statement -
I liked the movie. I liked it too.
I did not like the movie. I did not like it either.
Usage of Neither/So
The above sentences can be rephrased using neither and so. For example –
P1 – I got good marks.
P2 – So did I.
P1 – I did not get good marks.
P2 – Neither did I.
Using neither and so is more straightforward and less repetitive. Same as either, neither is also used as a reply for negative verb (in this case did not). Since neither itself implies in the negative, we put positive verb (did). More examples –
I do not want to have lunch. Neither do I.
I will not come tomorrow. Neither will I.
Another point to be noticed is that we should never say “So I am” or “Neither I did”. This would be an incorrect syntax.
2. Either as each
Sometimes, either can be used to represent each of the two options. For example,
a. There were flowers on either side of the road. This sentence means the same as “There were flowers on both sides of the road.”
b. There is a water vending machine at either end of corridor which means “There is a water vending machine on both the ends of the corridor.”
Either when used with or means one of the two available options. For example -
a. You can take either the icecream or the pizza. (This means you can't take both.)
b. Either you or me have to go and pick up the luggage. (Meaning one of us has to go)
Neither can be used alone or with 'nor'. For example -
Neither of us liked the movie or Neither me nor him liked the movie.
Neither of them has got a car
Note that when using neither, the verb that follows should be singular and not plural. In the example above, it would be incorrect to say Neither of them have got a car. Since we are talking about one of the two persons, use singular verb.
Tip – when in doubt, rephrase the sentence. Let's consider the above example itself.
Neither of them has got a car. ==> Neither he nor she has got a car ==> He has not got a car. She has not got a car.
When you break it down, you will know that we are talking about only one out of the two here, which is why we have to use singular verb. Few more examples -
a. Neither of us is interested in sports.
b. Neither of my parents is alive.
c. Neither of the jobs you told is interesting.
Both is used when both the given options are true. It is like a union. For example -
a. My aunt has two children. Both work in the US.
Here is a conversation that includes either, neither, both for you to get an overall idea -
A – Hey B. Did you like the show yesterday?
B – Yes.
A – So did I. Is either of you or your sister free tomorrow?
B – Yes, both of us are free. What is the matter?
A – Would you prefer going for a movie or some shopping?
B – Neither. We would rather stay at home and sleep.