Mia zia non è severa con le bambine.

With singular family members in standard Italian, the possessive usually appears without the article:

• mia zia = my aunt
• mio fratello = my brother
• nostra madre = our mother

So mia zia is the normal form here.

By contrast, with many other nouns, Italian normally does use the article with possessives:

• la mia macchina = my car
• il mio libro = my book

A learner should also know that the article can reappear with family words in some special cases, such as plurals or when the noun is modified:

• le mie zie = my aunts
• la mia cara zia = my dear aunt

Non è means is not.

• non = not
• è = is

So:

• Mia zia è severa = My aunt is strict
• Mia zia non è severa = My aunt is not strict

The accent on è matters because it distinguishes the verb è (is) from e (and).

• è = is
• e = and

So the accent is not optional here.

Because the adjective must agree with zia, which is feminine singular.

Agreement here is:

• zia = feminine singular
• severa = feminine singular adjective form

The adjective severo changes like this:

• severo = masculine singular
• severa = feminine singular
• severi = masculine plural
• severe = feminine plural

Examples:

• Mio zio è severo. = My uncle is strict.
• Mia zia è severa. = My aunt is strict.
• Le zie sono severe. = The aunts are strict.

Because this is a sentence with essere (to be), and severa is a predicate adjective describing the subject.

Structure:

• Mia zia = subject
• non è = verb
• severa = adjective describing the subject
• con le bambine = prepositional phrase

So the basic pattern is:

subject + essere + adjective

Examples:

• Lei è stanca. = She is tired.
• Il film è bello. = The film is beautiful.
• Mia zia non è severa. = My aunt is not strict.

In Italian, standard negation with non goes before the verb.

So:

• è severa = is strict
• non è severa = is not strict

This is one of the most basic Italian sentence patterns:

• Non parlo italiano. = I do not speak Italian.
• Non abbiamo tempo. = We do not have time.
• Mia zia non è severa. = My aunt is not strict.

English speakers sometimes want to put not after the verb because English does that, but Italian does not work that way here.

Con means with, but in sentences like this it often expresses the way someone behaves toward or with other people.

So severa con le bambine means:

• strict with the girls
• strict toward the girls

This is a very natural combination in Italian:

• essere gentile con qualcuno = to be kind to/with someone
• essere paziente con qualcuno = to be patient with someone
• essere severo con qualcuno = to be strict with someone

So con is the normal preposition here.

Italian often uses the definite article where English may or may not use it.

Here le bambine means the girls, referring to a specific group understood from context.

• le = feminine plural definite article
• bambine = girls

So:

• con le bambine = with the girls

If you removed the article, the phrase would usually sound incomplete or unnatural in this sentence.

Also note that bambine is feminine plural because:

• la bambina = the girl
• le bambine = the girls

The singular is bambina.

The endings help you recognize gender and number:

• bambina = feminine singular
• bambine = feminine plural

This is a very common pattern:

• ragazza / ragazze
• amica / amiche
• sorella / sorelle

So in le bambine, both the article le and the noun ending -e show that the noun is feminine plural.

In standard Italian, mia zia is the more normal choice.

La mia zia may sometimes be heard in regional or informal usage, but for a learner, mia zia is the safest and most standard form.

So if you are learning standard Italian, use:

• mia zia

not usually:

• la mia zia

Severa is a very natural word for strict here, especially in the sense of being strict with children.

Other adjectives exist, but they are not exact matches:

• rigida = rigid, strict, stiff
• dura = harsh, tough
• gentile = kind
• permissiva = permissive

So severa con le bambine is a normal and idiomatic way to express this idea.

The adjective would change to agree with the subject.

Examples:

• Mio zio non è severo con le bambine.
  My uncle is not strict with the girls.

• Le mie zie non sono severe con le bambine.
  My aunts are not strict with the girls.

• I miei zii non sono severi con le bambine.
  My uncles are not strict with the girls.

Notice the changes:

• è becomes sono in the plural
• severa / severo / severe / severi changes to match gender and number