Mater dicit sarcinas nimis graves esse et parvum viaticum satis esse.

Because after dicit in this sentence, Latin uses indirect statement: an accusative subject + infinitive.

So instead of saying:

• The bags are too heavy
• The small amount of travel money is enough

Latin puts the subjects into the accusative and the verbs into the infinitive:

• sarcinas ... esse = that the bags are ...
• parvum viaticum ... esse = that the small amount of travel money is ...

This construction is extremely common after verbs of saying, thinking, knowing, hearing, and so on.

For the same reason: this is indirect statement.

In direct statement, you would have:

• Sarcinae nimis gravēs sunt.
• Parvum viāticum satis est.

But after Mater dicit (Mother says), Latin changes those verbs to the infinitive:

• sarcinas nimis graves esse
• parvum viaticum satis esse

So esse here means to be, but in English we usually translate the whole structure as that ... are/is.

Because it agrees with sarcinas, which is plural.

• sarcinas = bags/luggage in the accusative plural
• graves = heavy, also plural

Latin adjectives must agree with the nouns they describe in gender, number, and case.

Since sarcinas is feminine accusative plural, graves is also accusative plural feminine.

Because viaticum here is a singular neuter noun.

It means something like:

• travel money
• travel allowance
• sometimes more generally provisions for a journey

So parvum viaticum means a small amount of travel money/provisions.

The adjective parvum agrees with viaticum:

• neuter
• singular
• accusative

Nimis means too or too much.

So:

• nimis graves = too heavy

It is an adverb modifying the adjective graves.

A useful contrast is:

• valde graves = very heavy
• nimis graves = too heavy

So nimis usually suggests excess, not just intensity.

Satis is an indeclinable word meaning enough or sufficiently.

Here it means:

• parvum viaticum satis esse = that the small amount of travel money is enough

Latin often uses satis with esse:

• satis est = it is enough
• in indirect statement: satis esse = to be enough / that it is enough

So even though English uses enough like an adjective, Latin often uses satis more like an adverbial idea with esse.

Because Latin usually does not use a separate word meaning that in this kind of sentence.

English says:

• Mother says that the bags are too heavy...

Latin instead uses the accusative-and-infinitive construction:

• Mater dicit sarcinas nimis graves esse...

So the idea of that is built into the grammar of accusative + infinitive. There is no need for a separate conjunction.

Et is joining two indirect statements:

1. sarcinas nimis graves esse
2. parvum viaticum satis esse

So the structure is:

• Mater dicit
  
  • [sarcinas nimis graves esse]
  • et
  • [parvum viaticum satis esse]

In English: Mother says that the bags are too heavy and that the small amount of travel money is enough.

Sometimes Latin can omit a repeated esse, especially in compact or poetic style, but in normal teaching examples and clear prose it is often kept.

So this sentence repeats esse because there are two separate statements:

• sarcinas nimis graves esse
• parvum viaticum satis esse

Repeating it makes the structure clearer.

The dictionary form is sarcina, -ae, a feminine noun.

In this sentence:

• sarcinas = accusative plural

So the forms are:

• nominative singular: sarcina
• nominative plural: sarcinae
• accusative plural: sarcinas

That accusative plural is used because sarcinas is the subject of the indirect statement.

Latin word order is much more flexible than English word order because Latin shows grammatical relationships through word endings.

So although English strongly prefers:

• Mother says that the bags are too heavy...

Latin can say:

• Mater dicit sarcinas nimis graves esse...

and still be clear because:

• sarcinas is accusative plural
• graves agrees with it
• esse marks the infinitive clause

The sentence is actually fairly natural Latin word order: the main verb dicit comes early, and then the two indirect statements follow.

A very literal breakdown is:

• Mater = Mother
• dicit = says
• sarcinas = the bags
• nimis graves = too heavy
• esse = to be
• et = and
• parvum viaticum = the small travel allowance / small amount of travel money
• satis = enough
• esse = to be

So, almost word-for-word:

Mother says the bags to be too heavy and the small travel allowance to be enough.

That sounds odd in English, but it helps show how the Latin grammar works.