Стигла груша коричнева.

Because they both agree with груша, and груша is a feminine singular noun.

In Ukrainian, adjectives change their endings to match the noun in:

• gender
• number
• case

Here everything is:

• feminine
• singular
• nominative

So:

• стиглий → стигла
• коричневий → коричнева

Their dictionary forms are:

• стиглий = ripe
• коричневий = brown

Dictionaries usually list adjectives in the masculine singular nominative form, so that is the form you normally look up.

In Ukrainian, the present-tense verb to be is usually omitted.

So instead of saying the exact equivalent of The ripe pear is brown, Ukrainian normally just says:

• Стигла груша коричнева.

The verb є can appear, but in simple everyday sentences it is often left out:

• Стигла груша є коричнева sounds much less natural than
• Стигла груша коричнева

Because the two adjectives are doing different jobs.

• стигла груша = ripe pear
  Here стигла directly describes the noun.

• груша коричнева = the pear is brown
  Here коричнева is part of the predicate: it tells you something about the pear.

So the full sentence means:

• [The ripe pear] [is brown].

If you put both adjectives before the noun:

• стигла коричнева груша

that would mean something more like:

• a ripe brown pear

That is a different structure.

All three words are in the nominative singular feminine.

• груша is the subject, so nominative makes sense.
• стигла agrees with груша, so it is also nominative feminine singular.
• коричнева is a predicate adjective, and here it is also in the nominative.

So this is a very useful beginner pattern:

• [adjective + noun] + [predicate adjective]

Ukrainian has no articles like a or the, so the sentence itself does not explicitly mark that.

Depending on context, it could correspond to:

• a ripe pear is brown
• the ripe pear is brown
• sometimes just ripe pear is brown in a very literal gloss

In natural English, you would usually choose a or the based on the situation.

No. Here стигла is an adjective meaning ripe.

That matters because стигла can also look like a past-tense feminine verb form from стигнути in other contexts. But in this sentence, it is clearly an adjective because it matches груша and forms the noun phrase:

• стигла груша = ripe pear

So here it is not she managed / she had time or anything verbal like that.

To some extent, yes, because Ukrainian word order is more flexible than English. But changing the order can also change the emphasis or even the structure.

For example:

• Стигла груша коричнева.
  = The ripe pear is brown.

• Коричнева груша стигла.
  = The brown pear is ripe.

Those are not the same thing. The adjective before the noun tends to belong closely to it.

So yes, word order is flexible, but it is not random.

The adjective endings would change to match the noun.

For example:

• Стиглий банан коричневий.
  = The ripe banana is brown.

• Стиглі груші коричневі.
  = The ripe pears are brown.

This is the same pattern, just with different agreement endings:

• feminine singular: стигла, коричнева
• masculine singular: стиглий, коричневий
• plural: стиглі, коричневі

A helpful stress guide is:

• СТИ-гла
• ГРУ-ша
• ко-РИЧ-не-ва

A rough English-friendly approximation is:

• STY-hla HROO-sha ko-RYCH-ne-va

A few pronunciation notes:

• Ukrainian г is not a hard English g. It is closer to a voiced h sound.
• Ukrainian и in стигла is not English ee. It is a shorter, more central vowel.
• ш is like English sh.

You could, but in most normal everyday Ukrainian it sounds less natural than leaving є out.

For simple present-tense identification or description, Ukrainian usually prefers:

• Стигла груша коричнева.

Using є is possible in some contexts, especially for emphasis, contrast, or a more formal tone, but beginners should usually learn the zero-copula pattern first.