Post laborem familia in horto sedet et vespertinum caelum spectat.

Because post is a preposition that normally takes the accusative case in Latin.

So:

• post = after
• laborem = accusative singular of labor

Together, post laborem means after work or after the work.

For an English speaker, this is worth noticing because English prepositions do not usually change the form of the noun after them, but Latin prepositions often do.

Familia is nominative singular, and it is the subject of both verbs.

So familia is the thing doing the actions:

• sedet = sits
• spectat = looks at / watches

That is why the verbs are in the third person singular: the subject is one familia.

Because grammatically familia is a singular noun, even though it refers to a group.

This works much like English family in sentences such as:

• The family sits in the garden

Latin is treating familia as one unit, so it uses singular verbs:

• familia sedet
• familia spectat

Also, in Latin familia can mean more than just parents and children; it can mean the whole household.

Because in takes the ablative when it means in or on in the sense of location.

So:

• in horto = in the garden

A very common contrast is:

• in + ablative = location, in/on
• in + accusative = motion into, into

For example:

• in horto sedet = he/she sits in the garden
• in hortum intrat = he/she enters into the garden

Because Latin has no definite article and no indefinite article.

That means Latin does not have separate words for:

• the
• a
• an

So familia can mean:

• the family
• sometimes a family, depending on context

Likewise:

• horto = in the garden or in a garden
• vespertinum caelum = the evening sky or an evening sky

The context tells you which English article makes the most sense.

Because once the subject is clear, Latin often leaves it unstated with the next verb.

So:

• familia ... sedet et spectat

means:

• the family sits and watches

Latin does not need to repeat familia because the same subject naturally continues across both verbs. English often works the same way:

• The family sits in the garden and watches the sky

Because caelum is the direct object of spectat.

The verb spectat means looks at, watches, or observes, and the thing being watched is put in the accusative case.

So:

• spectat caelum = watches the sky

In this sentence, the object is expanded by an adjective:

• vespertinum caelum = the evening sky

Both words are in the accusative because the whole phrase is the object of spectat.

Vespertinum is an adjective modifying caelum, so it must agree with it in:

• gender
• number
• case

Here:

• caelum is neuter singular accusative
• vespertinum is also neuter singular accusative

That is why the adjective has the form vespertinum.

A learner should notice that Latin adjectives change form to match the noun they describe, unlike English adjectives, which do not change.

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

Putting Post laborem first helps set the scene right away:

• After work, the family sits in the garden and watches the evening sky.

This kind of opening phrase is very natural in Latin. The sentence could be rearranged in other ways without changing the basic meaning, for example:

• Familia post laborem in horto sedet et vespertinum caelum spectat.

But the original order gives a nice sense of time first, then the main action.

Yes. In many contexts, Latin present tense can correspond to either English:

• simple present: sits, watches
• progressive: is sitting, is watching

So this sentence could be understood as:

• The family sits in the garden and watches the evening sky
• or The family is sitting in the garden and watching the evening sky

English chooses between those two forms more explicitly than Latin does. Latin often lets context decide.

Not always.

In Latin, familia often means the household, which can be broader than the modern English idea of a family. Depending on context, it may include:

• parents
• children
• slaves
• servants
• others belonging to the household

So in a Latin text, familia can sometimes feel a bit wider in meaning than English family. In this sentence, though, translating it as family is perfectly natural.