Она увидела объект.

Because this is the past tense feminine singular form of the verb увидеть (to see, perfective).

In Russian, past-tense verbs agree with the subject in gender and number:

• он увидел = he saw
• она увидела = she saw
• оно увидело = it saw
• они увидели = they saw

So since the subject is она (she), the verb must be увидела.

This is a question about aspect, which is very important in Russian.

• увидела comes from увидеть → perfective
• видела comes from видеть → imperfective

In this sentence, увидела suggests a completed event: she saw / caught sight of the object.

By contrast, она видела объект could mean something more like:

• she was seeing the object
• she saw the object (without emphasizing completion)
• she had seen the object / was familiar with seeing it, depending on context

So увидела объект is the more natural choice when talking about a single finished moment of noticing or seeing something.

Because it is the direct object, so it is in the accusative case. But for many masculine inanimate nouns, the accusative singular looks exactly like the nominative singular.

So:

• nominative: объект
• accusative: объект

That is normal.

Compare:

• Я вижу объект. = I see the object.
• Это объект. = This is an object.

The form stays the same.

If the noun were masculine animate, the accusative would often look different:

• Я вижу брата. = I see my brother.

Russian does not use articles like English a / an / the.

So объект can mean:

• an object
• the object

Which one is meant depends on context.

That is very normal in Russian. Learners often want to add a separate word for the, but Russian simply does not work that way.

This is a very normal, neutral word order:

• Она = subject
• увидела = verb
• объект = object

So it follows the familiar Subject–Verb–Object pattern.

Russian word order is more flexible than English, though. You can change it for emphasis:

• Она увидела объект. = neutral
• Объект она увидела. = emphasizes the object
• Увидела она объект. = more marked or stylistic

But the original version is the most straightforward one for a learner.

объект is pronounced roughly like ab-YEKT.

The stress is on the second syllable:

• объе́кт

The hard sign ъ does not have its own sound. Its job here is to separate the consonant before it from the vowel after it.

Because of ъ, the е is pronounced like ye rather than just e, and the previous consonant stays hard.

So объект is not pronounced as one smooth softened syllable; it has that little y sound:

• об-йект → more naturally ab-YEKT

The normal stress is:

• она́ уви́дела объе́кт

Word by word:

• она́ = stress on the last syllable
• уви́дела = stress on ви
• объе́кт = stress on е

Stress matters in Russian, so it is worth learning each word together with its stress pattern.

Yes, sometimes.

Russian often leaves out subject pronouns when the subject is clear from context. So in the right situation, you could say:

• Увидела объект.

and it could mean:

• She saw the object.

However, without context, that can feel less clear than Она увидела объект, especially for learners. Including она makes the subject explicit.

Yes, it is correct and natural, but it can sound a bit formal, technical, or context-dependent.

Depending on the situation, Russian might also use other nouns, such as:

• предмет = item, object, thing
• вещь = thing
• цель = target (if that is the intended meaning)

So объект is a good word, but it often suggests something like:

• an object of observation
• a physical object
• a target
• a site/facility, in some contexts

In your sentence, it is perfectly grammatical and natural.

Yes, very often увидеть can carry the sense of catching sight of or noticing something, especially because it is perfective.

So depending on context, Она увидела объект could suggest:

• she saw the object
• she spotted the object
• she noticed the object

The exact English translation depends on the situation, but the Russian form naturally suggests a single completed act of seeing.