Mater vas fragile in mensa ponit et ei aquam calidam addit.

Mater is in the nominative singular, which is the normal case for the subject of a sentence.

A few helpful points:

• mater means mother
• its dictionary form is mater, matris
• as a third-declension noun, its nominative singular does not have the very obvious -a ending that many first-declension nouns have

So in this sentence, mater is the one doing the actions: she ponit and addit.

Here vas is accusative singular, because it is the direct object of ponit: it is the thing being put somewhere.

It looks the same as the nominative because vas is a neuter noun:

• dictionary form: vas, vasis
• gender: neuter
• in Latin, neuter nouns often have the same form in nominative and accusative

So:

• nominative singular: vas
• accusative singular: vas

That is completely normal for a neuter noun.

Because fragile has to agree with vas.

The adjective is:

• fragilis, fragile = fragile

Since vas is:

• neuter
• singular
• accusative

the adjective must also be:

• neuter
• singular
• accusative

For this adjective, the neuter nominative/accusative singular form is fragile.

So:

• vas fragile = a fragile vessel

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

So a noun like vas can mean:

• a vessel
• the vessel

and the context tells you which is intended.

The same is true for:

• mater = mother or the mother
• mensa = table or the table
• aqua = water or the water

In Latin, in can mean either in or on, depending on the context.

With something like mensa (table), English normally says on the table, because a table is a surface. Latin still uses in.

So:

• in mensa = on the table

This is a very common thing for English speakers to notice, because Latin in covers a wider range than English in.

That is a very reasonable question.

A beginner often learns:

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

So you might expect in mensam.

But with verbs of placing, such as ponere, Latin can also use in + ablative to show the place where something is set. So in mensa ponit is acceptable for she puts it on the table.

A simple way to think about it:

• in mensam would stress movement onto the table
• in mensa can describe the place where the object is placed, on the table

So the sentence as given is not strange.

Both verbs are:

• present tense
• active voice
• indicative mood
• third person singular

So they mean:

• ponit = she/he/it puts
• addit = she/he/it adds

In this sentence, the subject is mater, so the natural meaning is:

• mother puts
• and adds

Their dictionary forms are:

• pono, ponere = to put
• addo, addere = to add

Latin often leaves out subject pronouns when they are not needed.

English usually says:

• she puts
• she adds

Latin can simply say:

• ponit
• addit

because the verb ending already tells you the subject is third person singular.

Then the noun mater makes it clear who that she is. So Latin does not need to repeat a separate word for she.

Ei is the dative singular form of the pronoun is, ea, id.

It can mean:

• to him
• to her
• to it

Here it refers back to vas, which is neuter, so it means to it.

A very important thing to notice is that the dative singular form ei is the same for masculine, feminine, and neuter. So even though vas is neuter, Latin still uses ei.

Because aquam is the direct object of addit, and calidam agrees with it.

The verb addere often works like this:

• thing added = accusative
• person or thing receiving it = dative

So in this sentence:

• ei = to it → dative
• aquam calidam = warm water → accusative

And because aqua is feminine singular accusative, the adjective must match:

• aquam
• calidam

Latin adjective placement is much freer than English adjective placement.

In English, we usually say:

• fragile vessel
• warm water

In Latin, both of these are normal:

• vas fragile
• fragile vas
• aquam calidam
• calidam aquam

The important thing is not the position, but the agreement:

• same gender
• same number
• same case

So fragile matches vas, and calidam matches aquam, no matter where they stand.

Latin word order is much more flexible because case endings show what each word is doing.

English depends heavily on word order:

• She adds warm water to it

Latin can arrange the words more freely because the endings already show the roles:

• ei = dative, to it
• aquam = accusative, direct object
• calidam = adjective agreeing with aquam
• addit = the verb

So ei aquam calidam addit literally looks more like:

• to it warm water she adds

That sounds odd in English, but it is perfectly natural in Latin. Short pronouns like ei also often appear early in the clause.