Adverb

[jack]

Are these correct? What do they mean?

1. This router has a range of 100 meters indoors. (Why do I need to add a -s for 'indoor'?)
2. This router has a range of 100 meters indoor. (If this is incorrect, why?)

3. This router has a range of 100 meter indoors. (Do I need to add a -s for 'meter' If so, why?)
4. This router has a range of 100 meters indoors.

Are these correct? What do these mean?
5. Indoor use only.
6. Indoors use only. (If this is wrong, why?)

[Casiopea]

If it answers the question Where?, then it's an adverb.

Q: Where does this router have a range of 100 meters?
A: Indoors.

If it answers the question What?, then it's a noun.

Q: A 100 what?
A: A 100 meters. ('100' is more than one, and it modifies 'meters', so 'meters' must take -s)

Adverbs cannot modify nouns.

indoor use (adjective + noun) e.g., It has many indoor uses.
*indoors use (adverb + noun)

[jack]

If it answers the question What?, then it's a noun.

Q: A 100 what?
A: A 100 meters. ('100' is more than one, and it modifies 'meters', so 'meters' must take -s)

1. Do you have a hundred apples? (So 'A 100 what' works like this?)

I don't really get this part:

Adverbs cannot modify nouns.

indoor use (adjective + noun) e.g., It has many indoor uses.
*indoors use (adverb + noun)

So this is wrong?
2. It has many indoor uses. (Why is it wrong?)

*indoors use (adverb + noun)

3. What do you mean by this?

[Casiopea]

Both 1. and 2. are correct. 'indoor' is an adjective. Adjectives modify nouns; e.g., indoor (Adjective) + uses (Plural noun). 'indoors' is an adverb. Adverbs cannot modify nouns; e.g., *indoors (Adverb) uses (Plural Noun).

[jack]

Thanks.

1. This router has a range of 100 meters indoors. (This sentence is correct right?)

Is this correct as well?
2. This router has a range of a 100 meters indoors. (So is 'a' omitted in #1? It sounds kind of awkward with 'a' here though, why?)

Is this incorrect?
3. This router has a range of 100 meter indoors.

[Casiopea]

1. 100 meters (one-hundred meters)
=> Note, 'one' is synonymous with 'a'. Use one or the other, not both.

2. a 100 meters (a hundred meters)
=> Note, 'a' replaces 'one'. 'one' is not spoken.)

3. is incorrect. We determined that already, though, right? 100 is plural so 'meters' should be plural. 'a' replaces 'one'. 'a' does not refer to 'meters'. It refer to 'hundred'.

one-hundred ~ a hundred, written as either 'a 100' or '100'.
two-hundred
three-hundred

[jack]

Thanks.

What about this? How do I know if it's needs to be an adverb or noun?
1. This product has a range of 100 meters for indoor.
2. This product has a range of 100 meters for indoors.

[jack]

What do these mean? How do I use the word 'onwards'?
1. Sentence 99. and onward have me confused.
2. Sentence 99. and onwards have me confused.

3. We sailed onwards in a westerly direction.
4. We sailed onward in a westerly direction.

[Casiopea]

Thanks.

What about this? How do I know if it's needs to be an adverb or noun?
1. This product has a range of 100 meters for indoor.
2. This product has a range of 100 meters for indoors.

You're welcome.

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".

Note, You have two verbs here: *it's needs. Try, it needs.

[Casiopea]

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