Itaque sapiens femina nec felicibus tantum, sed etiam infelicibus adest, et omnes benignitate vincit.

Itaque means and so, therefore, accordingly. It connects this sentence to what came before and shows that it is a conclusion or result.

So it is not part of the core subject-verb structure; it is a connecting adverb.

Sapiens is a third-declension adjective with the same nominative singular form for masculine and feminine.

So:

• sapiens vir = a wise man
• sapiens femina = a wise woman

Even though femina is feminine, the adjective does not need a special feminine nominative singular ending here.

Both words are in the nominative singular:

• sapiens = nominative singular
• femina = nominative singular

That makes sapiens femina the subject: the wise woman.

The verbs also match a singular subject:

• adest = she is present / she helps
• vincit = she conquers / surpasses / wins over

This is the Latin equivalent of not only ... but also ...

Here it means:

• nec felicibus tantum = not only to the fortunate
• sed etiam infelicibus = but also to the unfortunate

A very literal breakdown is:

• nec = not
• tantum = only
• sed etiam = but also

So the sentence is contrasting two groups and saying the wise woman is there for both.

In this kind of correlative expression, Latin often uses nec or neque with tantum, followed by sed etiam.

So nec ... tantum, sed etiam ... is a normal idiomatic way to say not only ... but also ...

You should think of it as a set phrase rather than translating each word too mechanically.

They are dative plural here.

That is because adest is built with the dative of the person someone is present to, near, or helpful to.

So:

• felicibus adest = she is present to / helps the fortunate
• infelicibus adest = she is present to / helps the unfortunate

Formally, felicibus and infelicibus could also be ablative plural in isolation, but here the verb adest makes the dative meaning clear.

Latin often uses adjectives substantively, meaning the adjective stands by itself as a noun.

So:

• felicibus = the fortunate people
• infelicibus = the unfortunate people

English can do this too, as in the rich, the poor, the innocent.

Adest is from adsum, adesse, literally to be present. But with a dative, it often has the sense to be there for, to support, or to help.

So here it is more than physical presence. It suggests that the wise woman is available, supportive, and helpful to both kinds of people.

Because omnes is the direct object of vincit.

• vincit = she conquers / surpasses / wins over
• omnes = all people / everyone

Since vinco takes a direct object, that object goes in the accusative:

• omnes = accusative plural

If it were omnibus, that would be dative or ablative plural, which would not fit this verb here.

The basic meaning of vinco is to conquer, defeat, overcome. But in a sentence like this, it often has a broader sense such as:

• surpasses
• outdoes
• wins over

So omnes benignitate vincit does not have to mean military conquest. It means that by her kindness she is superior to others, or that she wins everyone over through kindness.

Benignitate is an ablative of means (also called instrument).

It answers the question by means of what?

• benignitate vincit = she conquers / surpasses / wins over by kindness

So the idea is that kindness is the means or instrument by which she does this.

Latin often leaves the subject pronoun unstated because the verb ending already tells you the person and number.

Both verbs are third person singular:

• adest = he/she/it is present
• vincit = he/she/it conquers

Since the subject sapiens femina is already given, Latin does not need to add ea for she.

Latin word order is more flexible than English word order, because case endings show the grammatical roles.

Still, the order here is meaningful and stylistic:

• sapiens femina puts the subject near the front
• nec felicibus tantum, sed etiam infelicibus sets up a balanced contrast
• omnes benignitate vincit ends with the strong verb vincit

So the order helps with emphasis and rhythm, even though the grammar is mainly shown by endings rather than position.