Filii respondent: "Nunc foris currimus, sed soror intus legit."

Filii is the nominative plural of filius (son).

• filius = son (singular, subject form)
• filii = sons (plural, subject form)

The -ii ending is normal for some masculine nouns in -ius in the nominative plural. So:

• filius → filii
• servus → servi (no double i because the singular doesn’t end in -ius)

In this sentence, filii is the subject of respondent: The sons reply…

• respondent: 3rd person plural, present tense
  
  • they reply / they are replying
• currimus: 1st person plural, present tense
  
  • we run / we are running
• legit: 3rd person singular, present tense
  
  • he/she reads / is reading

So:

• filii respondent → the sons reply
• currimus → we run / we are running
• soror … legit → the sister reads / is reading

Latin usually does not need a separate subject pronoun (like I, you, we) because the verb ending already shows the person and number.

• currimus = we run / we are running
  The ending -mus tells you we.

You could add nos (we) for emphasis:

• Nunc nos foris currimus = Now we are the ones running outside

But in normal, neutral Latin, currimus alone is enough.

Inside the speech, the sons are describing two different subjects:

• Nunc foris currimus → Now we are running outside
  Subject: we = the speakers (the sons)
• sed soror intus legit → but (our) sister is reading inside
  Subject: soror (sister), a different person

Latin can change subjects mid-sentence just as English can. You identify the subject from:

• A noun in the nominative (soror), or
• The verb ending (currimus ⇒ we)

Here foris and intus are adverbs of place:

• foris = outside, outdoors
• intus = inside

They work like English adverbs outside / inside, not like prepositions:

• foris currimus = we run outside
• intus legit = she reads inside

They do not need a noun after them.
Compare:

• in horto currimus = we run in the garden (in is a preposition, takes a noun)
• foris currimus = we run outside (foris is an adverb, stands alone)

Yes, you can say currimus foris. Latin word order is quite flexible.

Both:

• Nunc foris currimus
• Nunc currimus foris

mean Now we are running outside.

Placing foris before currimus might slightly highlight outside, but in a short simple sentence the difference is minimal. Latin often puts adverbs either before or after the verb without a strong change in meaning.

Both currimus and legit are in the present indicative.

Latin present tense covers both English simple present and present progressive:

• currimus = we run or we are running
• legit = she reads or she is reading

The choice between we run and we are running is made when translating into English, based on what sounds more natural in context. Here, we are running / she is reading fits well with nunc (now).

Forms like legit can be ambiguous in writing:

• Present: legit = he/she reads
• Perfect: légit (different vowel length and stress) = he/she has read / read

In normal textbook/classroom Latin:

• If nothing suggests a completed past action, legit in a present-time sentence with nunc is taken as present: she reads / is reading.

So here, with nunc and a clearly present-time description, legit is understood as present tense, not has read.

Soror is the nominative singular of soror, sororis (sister).

• Nominative singular (soror) is used for the subject of the verb.
  
  • soror intus legit = the sister is reading inside

Sororem would be the accusative singular, used for the direct object (the thing affected by the verb), like:

• filii sororem vident = the sons see (their) sister

In your sentence, soror is the doer of the action legit, so nominative soror is correct.

The colon and quotation marks here are modern editorial punctuation, not an ancient Latin rule. Ancient texts originally had much less standardized punctuation.

The structure is:

• Filii respondent: = The sons reply:
• followed by their exact words:
  Nunc foris currimus, sed soror intus legit.

Latin often introduces direct speech with a verb of saying or replying (inquit, dicit, respondent, etc.), and modern editors use punctuation (colon, quotes) to make that clear, just like in English.

In English, the progressive form uses to be (is reading, are running). Latin does not form the present tense this way.

• Latin simply uses the present tense of the main verb:
  • legit = she reads / she is reading
  • currimus = we run / we are running

So Latin does not say soror est legens for normal she is reading; that would sound unusual or overly literal. Instead, soror legit covers both ideas.

If there is only one son, the subject and its verb outside the quote would change to singular:

• Filius respondet: … = The son replies: …

Inside the quoted sentence, currimus still means we run, so that would imply that the son is speaking as part of a group (we are running). If you want him to say I am running, you would change currimus:

• Filius respondet: Nunc foris curro, sed soror intus legit.
  = The son replies: Now I am running outside, but my sister is reading inside.

Both orders are possible and both mean but (our) sister is reading inside.

• sed soror intus legit
• sed soror legit intus

Latin allows adverbs like intus before or after the verb. The change in emphasis is minor in a simple sentence:

• Putting intus earlier can slightly highlight inside, but it is subtle.
• Both are correct and natural Latin.