Pluvia gravis cadit; ideo pueri domi manent.

In Latin, adjectives can come either before or after the noun much more freely than in English. So pluvia gravis means heavy rain, even though the adjective comes second.

What matters most is agreement, not position:

• pluvia = feminine singular nominative
• gravis = feminine singular nominative

Because they match, the learner can see that gravis describes pluvia.

Because both words are in the nominative singular, which is the usual case for the subject.

Also, the verb cadit is third person singular, so it matches a singular subject:

• pluvia gravis = singular
• cadit = it falls/is falling

So the grammar points to pluvia gravis as the subject.

Cadit is:

• present tense
• active voice
• indicative mood
• third person singular

It comes from cadere, meaning to fall.

So cadit means falls or is falling, depending on context.

Latin normally has no articles. It does not have separate words that exactly match English the, a, or an.

So:

• pluvia gravis can mean heavy rain, the heavy rain, or a heavy rain, depending on context.
• pueri can mean boys or the boys.

When translating into English, you add the article that sounds natural.

Ideo means therefore, for that reason, or so. It is an adverb.

It connects the two ideas:

• heavy rain is falling
• therefore the boys stay at home

So it shows result or consequence.

Pueri is the nominative plural of puer, meaning boy.

It is the subject of manent because:

• pueri is nominative plural
• manent is third person plural

Those forms match, so pueri is the subject: the boys stay/remain.

Manent is:

• present tense
• active voice
• indicative mood
• third person plural

It comes from manere, meaning to remain, to stay, or to continue.

So here it means they stay or they remain.

Because manere does not just mean to be. It specifically means to remain or to stay.

So domi manent means:

• they stay at home
• or more literally, they remain at home

That is more precise than just saying they are at home.

Domi means at home. It is a special form called the locative, used with a small number of words, especially places like home.

So:

• domi = at home

Latin can also use prepositional phrases such as in domo, but domi is the normal idiomatic way to say at home.

This is one of those forms that learners usually just memorize:

• domi = at home
• domum = homeward / to home
• domo = from home

No. Latin word order is much freer than English word order because Latin uses endings to show how words function.

So the sentence could be rearranged in various ways and still mean roughly the same thing, for example:

• Gravis pluvia cadit; ideo pueri domi manent.
• Pueri ideo domi manent, quod pluvia gravis cadit.

However, the original order is clear and natural:

• first the cause
• then the result

The semicolon separates two closely connected complete thoughts:

• Pluvia gravis cadit
• ideo pueri domi manent

In English, you might also see:

• Heavy rain is falling, so the boys stay at home.
• Heavy rain is falling; therefore the boys stay at home.

So the semicolon helps show that the second clause follows logically from the first.

Yes, in this context gravis means heavy or severe. Its basic sense is something like weighty, serious, or heavy, but with weather and similar expressions it often becomes heavy or intense in English.

So pluvia gravis is a natural way to express heavy rain.

Yes. The Latin present tense often covers both a simple present and a progressive present in English.

So cadit can be translated as:

• falls
• is falling

Likewise, manent can be:

• stay
• are staying
• remain

The best English choice depends on context and style.