Cantharus et scyphus in mensa sunt.

Because the subject is compound: cantharus et scyphus.

Each noun by itself is singular, but two singular nouns joined by et mean more than one thing together, so Latin uses the plural verb:

• est = is
• sunt = are

So cantharus et scyphus ... sunt is exactly what you would expect.

They are both in the nominative singular.

That is the case normally used for the subject of the sentence, and here these are the things that are on the table.

So:

• cantharus = nominative singular
• scyphus = nominative singular

They are the dictionary form you would usually learn first.

Because in can take different cases depending on the meaning.

• in
  • ablative = location, meaning in/on/at
• in
  • accusative = motion into or onto something

Here the sentence describes where the objects are, not movement toward the table, so Latin uses the ablative:

• in mensa = on the table / in the table area

If the idea were movement onto the table, you would expect in mensam instead.

Yes.

Latin in with the ablative can correspond to several English prepositions depending on context, including in, on, and sometimes at.

With mensa meaning table, natural English usually says on the table, even though Latin still uses in.

So this is a good example of why you should not match Latin prepositions to English ones too mechanically.

Because Classical Latin does not have articles like English does.

A Latin noun by itself can mean:

• a
• an
• the

depending on context.

So cantharus could be translated as a cantharus or the cantharus, depending on what the surrounding context suggests. The same is true for scyphus and mensa.

No. Latin word order is much more flexible than English word order.

Because the noun endings show what each word is doing, Latin can move words around more freely for emphasis or style.

This sentence is a perfectly normal arrangement:

• Cantharus et scyphus in mensa sunt

But Latin could also say things like:

• In mensa cantharus et scyphus sunt

The basic meaning stays the same, though the emphasis may shift slightly. Putting sunt near the end is very common in Latin.

Et means and.

It simply joins two words of the same kind here:

• cantharus et scyphus = the cantharus and the scyphus

It is the most basic and common Latin word for and.

Latin also has other ways to join words, such as -que, but et is the straightforward choice here.

They are:

• cantharus: masculine, second declension
• scyphus: masculine, second declension
• mensa: feminine, first declension

So even though cantharus and scyphus are Greek loanwords, they are being used with normal Latin case endings.

A learner might recognize:

• cantharus, canthari
• scyphus, scyphi
• mensa, mensae

It would normally use in with the accusative.

So:

• in mensa = on the table / location
• in mensam = onto the table / motion toward

For example, a sentence about movement might say something like:

• Cantharus et scyphus in mensam ponuntur
  = The cantharus and the scyphus are being placed onto the table

So the case after in tells you whether the idea is location or motion.

In a common Classical pronunciation, roughly:

• cantharus = KAN-tha-rus
• et = et
• scyphus = SKÜ-phus or, in many classrooms, approximately SKI-phus
• in mensa = in MEN-sa
• sunt = soont

A few useful points:

• c is always hard, like k
• sc here sounds like sk
• y represents a Greek sound that English does not really have, so many learners approximate it

So even if exact pronunciation varies by classroom tradition, the important grammar of the sentence stays the same.