Praefurnium fumum habet.

You know mainly from the case endings, not just from word order.

• praefurnium is the subject
• fumum is the direct object
• habet is the verb, has

So the structure is:

• praefurnium = the thing doing the having
• fumum = the thing being had
• habet = has

In Latin, endings usually tell you each word’s job in the sentence more clearly than position does.

Because fumum is the accusative singular, and the direct object of habet must be in the accusative.

The basic form is:

• fumus = smoke, as a subject
• fumum = smoke, as a direct object

Compare:

• Fumus venit. = Smoke comes.
  Here fumus is the subject.

• Praefurnium fumum habet. = The furnace has smoke.
  Here fumum is the object.

So the ending changes because the word’s grammatical role changes.

Habet is:

• 3rd person singular
• present tense
• active voice
• from the verb habere = to have

So habet means he/she/it has.

Because the subject here is a thing, the natural English translation is it has or simply has with the noun:

• praefurnium ... habet = the furnace has ...

Latin does not have articles like English the and a/an.

So praefurnium can mean:

• the furnace
• a furnace

And fumum can mean:

• smoke
• the smoke
  depending on context

You choose the best English article from the situation, not from a separate Latin word.

Because the same ending can mean different things for different kinds of nouns.

Here:

• praefurnium is a neuter noun
• fumus is a masculine noun

In the second declension:

• a neuter nominative singular often ends in -um
• a masculine accusative singular often ends in -um

So:

• praefurnium = nominative singular neuter
• fumum = accusative singular masculine

They look similar, but they are not the same form grammatically.

Yes. Latin word order is much more flexible than English word order.

You could also see:

• Fumum praefurnium habet.
• Praefurnium habet fumum.

The core meaning would stay the same because the endings still show the roles.

That said, subject + object + verb is a very common neutral pattern in Latin, so Praefurnium fumum habet is a very natural basic order.

Because the verb ending already includes the subject information.

Habet already means he/she/it has. So Latin usually does not need to add a separate pronoun unless there is special emphasis.

English often says:

• It has smoke

Latin can simply say:

• fumum habet

If the noun subject is already stated, as in Praefurnium fumum habet, there is even less reason to add a pronoun.

It is singular.

You can tell from two things:

1. The noun form praefurnium here is singular.
2. The verb habet is also singular: has, not have.

So the sentence is talking about one furnace, not several.

You would usually look them up under their dictionary forms:

• praefurnium, praefurni(i), n.
• fumus, fumi, m.
• habeo, habere, habui, habitum

A beginner-friendly way to think of that is:

• nouns are usually looked up in the nominative singular
• verbs are usually looked up in the 1st person singular present form

So:

• fumum must be traced back to fumus
• habet must be traced back to habeo

In a simple classroom-style Classical Latin pronunciation, you could say it roughly like this:

pry-FOOR-nee-um FOO-mum HAH-bet

A few helpful points:

• ae in prae- sounds like English eye
• u is like oo in food
• c is always hard in Classical Latin, though there is no c here
• habet is pronounced with a clear h

A more careful syllable breakdown would be:

• prae-fur-ni-um
• fu-mum
• ha-bet