Modspilleren smiler.

In Danish, the definite article is usually added to the end of the noun as a suffix.

• en modspiller = an opponent
• modspilleren = the opponent

So where English says the opponent, Danish often says just one word: modspilleren.

Because spiller is a common-gender noun in Danish.

For singular definite nouns:

• common gender usually takes -en
• neuter usually takes -et

So:

• en spiller → spilleren
• not spilleret

Since modspiller is built on spiller, it keeps the same gender and therefore also takes -en: modspilleren.

Yes. Danish very often combines related nouns or prefixes into a single written word.

Here:

• mod- = opposing / counter-
• spiller = player

Together they form modspiller. Then the definite ending is added:

• modspiller
• modspilleren

Writing it as two words would normally be wrong.

Smiler is the present tense of smile.

The usual present-tense ending in Danish is -r:

• smile = infinitive
• smiler = present tense

Depending on context, Danish present tense can correspond to English:

• smiles
• is smiling

So this form does not by itself force a difference between simple present and present progressive.

Because Danish verbs do not change according to person or number in the present tense.

You get the same form with all subjects:

• jeg smiler
• du smiler
• han smiler
• vi smiler
• de smiler

So smiler stays the same no matter who is doing the action.

It is the normal Danish main-clause pattern: subject + verb.

• Modspilleren = subject
• smiler = verb

But Danish is a V2 language, which means the finite verb usually comes in the second position in a main clause. So if you move another element to the front, the verb still stays second:

• Nu smiler modspilleren. = Now the opponent is smiling.
• I dag smiler modspilleren. = Today the opponent is smiling.

That is an important Danish word-order rule.

Usually, no—not in the plain, ordinary sense.

For a simple definite noun, Danish normally uses the suffix form:

• modspilleren = the opponent

Using den is typical:

• with an adjective: den stærke modspiller = the strong opponent
• or as a demonstrative sense closer to that opponent

So for this sentence, modspilleren is the normal form.

A useful mini-paradigm is:

• en modspiller = indefinite singular
• modspilleren = definite singular
• modspillere = indefinite plural
• modspillerne = definite plural

Learning nouns in these related forms is very helpful, because Danish uses endings much more than English does for definiteness.