Pluvia pueros impedit, ne in horto ludant.

Because pluvia is the thing doing the action of impedit. The rain is what prevents the boys from playing.

So:

• pluvia = nominative singular
• nominative = the usual case for the subject

Latin relies on case endings, not word order alone, to show this.

Latin has no definite or indefinite article. It does not have separate words for the or a/an.

So depending on context:

• pluvia can mean rain or the rain
• pueros can mean boys or the boys

English has to choose an article, but Latin does not.

Because pueros is the accusative plural, and here it is the direct object of impedit.

The sentence says that the rain prevents the boys, so the boys are receiving the action of the verb.

• pueri = nominative plural, the boys as subject
• pueros = accusative plural, the boys as object

So pueros is exactly the form we expect after impedit.

Impedit is:

• 3rd person singular
• present tense
• active voice
• indicative mood

It comes from impedio, impedire, meaning to hinder, to prevent, or to obstruct.

It is 3rd singular because its subject, pluvia, is singular.

After verbs of preventing, hindering, or stopping, Latin commonly uses ne + subjunctive.

So:

• impedit, ne... = prevents ... from ...-ing

A very literal sense is something like:

• the rain hinders the boys, so that they do not play in the garden

But in natural English we usually say:

• the rain prevents the boys from playing in the garden

Here ne does not just mean a simple standalone not. It is part of a standard Latin construction used after verbs like impedio.

Because it is in a clause introduced by ne after a verb of preventing: impedit, ne...

That construction normally takes the subjunctive in Latin.

So ludant is:

• present subjunctive
• 3rd person plural
• from ludo, ludere

The plural makes sense because its understood subject is the boys.

Because ludunt would be the present indicative: they play.

But after impedit, ne..., Latin does not use the indicative. It uses the subjunctive, so we get ludant.

Compare:

• ludunt = they play
• ludant = they may play / should play / in this construction, simply the subjunctive form required after ne

So the choice is grammatical, not a change in the basic idea of playing.

The subject is understood from the context: the boys.

Latin often leaves pronouns unstated when the meaning is clear. Here the sentence means that the rain prevents the boys from playing, so the understood subject of ludant is the same group.

You could think of it as:

• Pluvia pueros impedit, ne pueri in horto ludant.

But Latin does not need to repeat pueri, because it is already obvious.

Because in with the ablative usually means in or on in the sense of location.

So:

• in horto = in the garden

If there were movement into the garden, Latin would usually use in + accusative:

• in hortum = into the garden

Since the boys are being prevented from playing in the garden, not from going into the garden, in horto is correct.

Latin word order is more flexible than English word order because the case endings already show the grammatical roles.

This sentence is perfectly natural as written:

• Pluvia pueros impedit, ne in horto ludant.

It starts with pluvia, which gives the cause first, then pueros, the people affected, then impedit, and finally the ne clause explaining what is being prevented.

A different order could still be grammatical, but it might sound slightly different in emphasis.

Normally, no. After verbs like impedio, Latin typically uses:

• ne
• sometimes quominus

So with impedit, ne is the standard and expected construction.

For that reason, ne in horto ludant is much more idiomatic Latin than an ut non clause here.