Adverb

[jack]

indoor is an adjective, and indoors is an adverb. Neither are nouns, and neither occur with a preposition. Sentences 1. and 2. are incorrect. Try,

3. This product has a range of 100 meters for indoor (adjective) use (noun).
=> preposition "for" + noun phrase "indoor use".

Thanks. This is very useful.

onward and onwards are one and the same word. Without -s is more common these days.

1. Onward. (This can be an adjective and adverb right?)
2. Onwards. (This is an adverb only and you're saying it doesn't matter which one I use?)

[Casiopea]

Thanks. This is very useful.

1. Onward. (This can be an adjective and adverb right?)
2. Onwards. (This is an adverb only and you're saying it doesn't matter which one I use?)

That's correct.

[jack]

Are these correct? What do they mean?

1. They are going to do something after.
2. They are going to do something afterwards.

[jack]

What do these mean?

1. They talk so loud.
2. They talk so loudly.

Thanks.