In mensa acetum et piper parata sunt.

Here mensa is in the ablative singular, because in takes the ablative when it means in or on in a static sense, showing location rather than motion.

So in mensa means on the table or in the table area/context, depending on context, though in normal English on the table is the natural translation.

A useful detail: if macrons are written, this would be in mensā. Without macrons, mensa can look the same as the nominative form.

Because there is no motion toward the table.

Latin often uses:

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

So:

• in mensā = on the table
• in mensam = onto the table / into the table area

In this sentence, the vinegar and pepper are already there, so Latin uses in + ablative.

Yes, acetum et piper is the subject.

This confuses many learners because both nouns are neuter singular, and in Latin the nominative and accusative forms of neuter nouns are the same.

So:

• acetum can be nominative singular or accusative singular
• piper can also be nominative singular or accusative singular

You know they are the subject here because they agree with parata sunt, which is plural and refers to them.

They are nominative singular forms, joined by et.

Individually, each noun is singular:

• acetum = vinegar
• piper = pepper

Together they make a compound subject: vinegar and pepper.

Even though each noun is singular, two singular nouns joined by and make a plural idea, which is why the verb is plural.

Because acetum et piper together form a plural subject.

Parata agrees with the whole compound subject, not with just one noun. Since both nouns are neuter, the participle is neuter plural:

• singular neuter: paratum
• plural neuter: parata

So parata means prepared in a form that agrees with acetum et piper together.

For the same reason: the subject is plural in sense.

Even though acetum and piper are each singular nouns, they are joined by et, so Latin treats them as they, not it.

So:

• one thing: est
• two or more things: sunt

That is why Latin says parata sunt, not parata est.

Parata sunt is the perfect passive form of parare.

It is made from:

• parata = the perfect passive participle
• sunt = they are

Together, this literally gives they have been prepared.

Depending on context, English may translate it in different ways:

• have been prepared
• are prepared
• are ready

So this is one of those Latin forms where the grammar is clear, but the best English wording depends on context.

Because the words it agrees with, acetum and piper, are both neuter.

Latin adjectives and participles must agree with the nouns they describe in:

• gender
• number
• case

Since the compound subject is:

• nominative
• plural
• neuter

the participle must also be:

• nominative
• plural
• neuter

So parata is exactly the expected form.

Latin word order is much more flexible than English word order because the endings show how words function.

This sentence puts the location first:

• In mensa = On the table
• acetum et piper = subject
• parata sunt = verb phrase

That order can sound natural in Latin, especially if the speaker wants to set the scene first: On the table, vinegar and pepper are ready / have been prepared.

English relies much more on position, while Latin relies much more on inflection.

Latin has no definite article like English the.

So a noun like mensa can mean:

• a table
• the table

and context tells you which is meant.

The same is true for acetum and piper. Latin leaves that unstated unless the context makes it important.

So learners should not expect every English the to have a separate Latin word.

Literally, in often means in, but in Latin it can also be used where English prefers on, especially with surfaces or places.

So in mensā can naturally be understood as on the table.

This is a good reminder that prepositions do not match perfectly from one language to another. You should learn the Latin usage itself, not assume it will line up exactly with English.