H me with these

Hi,

What are the differences for these two kinds of words? Give me some practical examples.

1. sport vs sports I used to play one sport, but now I play three sports.

When we speak generally, we usually speak of 'sport', eg 'Sport is good for your health'. But, 'sports' can also be used in this way.

2. parent vs parents. It's just singular/plural. I had two parents, but one died. Now I have one parent.

Additionally, can you help me with these?

3. ... the auxiliary "will" takes base form of the verb ... (Does it require no articles?)

Can the colored word be "no article"? Yes, in fact I prefer it. Can the determiner ??? "no" take on a singular noun? Yes

4. Do you need commas at the underlined parts? I think they don't need there. They shouldn't be there.

(the sentences are from the posts.)

The proper introduction is, ???" ... and now, please welcome Imago!"

So similary, in the case of Smelly Rose, they should be introduced as, ???" ... and now, please welcome Smelly Rose."      

Best wishes, Clive

Hi,

Thank you for the fetching. This is meant to show appreciation. You're welcome.

In regard to No.3, is the phrase "base form" a countable noun or an uncountable noun? Why no article there? I see the sentence that contained this as written in terse, almost 'point' form. If I were rewriting it in more 'careful' English, I'd say 'the base form'. 

Best wishes, Clive