Защитный уголок лежит на столе.

Literally, it means protective corner or protective corner piece.

• защитный = protective
• уголок = literally little corner, but in real usage it can mean a corner piece, corner guard, or some small object connected with a corner

So in this sentence, защитный уголок is best understood as a physical item, not just an abstract corner.

Угол means corner or angle in the basic sense.

Уголок is a very common noun formed with a diminutive suffix. Depending on context, it can mean:

• a small corner
• a little corner
• a corner piece
• a specific object associated with a corner

In many practical contexts, especially with objects, уголок sounds more like the name of a thing than just the geometric idea of a corner. So защитный уголок can refer to a protective corner guard.

Because it is an adjective agreeing with уголок.

Here, уголок is:

• masculine
• singular
• nominative case

So the adjective must also be:

• masculine
• singular
• nominative

That gives защитный.

A few comparison examples:

• защитный уголок — masculine singular
• защитная накладка — feminine singular
• защитное стекло — neuter singular
• защитные уголки — plural

A very common clue is the ending.

Уголок ends in a consonant, and nouns that end in a consonant are usually masculine in Russian.

So:

• уголок → masculine
• therefore защитный must also be masculine

This is one of the most useful gender patterns in Russian.

Лежит is the 3rd person singular of лежать, which means to lie or to be lying.

Russian often uses different verbs depending on an object's position:

• лежать = to lie
• стоять = to stand
• сидеть = to sit

So if something is resting horizontally on a surface, Russian often says it lies there.

That is why:

• Книга лежит на столе. = The book is lying on the table.
• Защитный уголок лежит на столе. = The protective corner piece is lying on the table.

In English, we often just say is on the table, but Russian likes to specify posture more often.

Usually no, not in this sentence.

Стоит means is standing. It is used for things that are upright or conceptually standing:

• Бутылка стоит на столе. = The bottle is standing on the table.
• Лампа стоит на столе. = The lamp is standing on the table.

But a small flat object like a защитный уголок would normally be thought of as lying, not standing, so лежит is the natural choice.

Because this sentence describes location, not motion.

Russian uses different cases after на depending on meaning:

• на столе = on the table → location
• на стол = onto the table → motion toward the table

Compare:

• Защитный уголок лежит на столе. = The protective corner piece is on the table.
• Я положил защитный уголок на стол. = I put the protective corner piece onto the table.

So here на столе is correct because the object is already there.

It is the prepositional case, singular.

The basic form is:

• стол = table

After на when it means on in the sense of location, Russian commonly uses the prepositional:

• на столе = on the table

Other examples:

• в доме = in the house
• на полу = on the floor
• в комнате = in the room

So столе is the prepositional singular form of стол.

Russian has no articles like English the and a.

So Защитный уголок лежит на столе could mean:

• The protective corner piece is lying on the table
• A protective corner piece is lying on the table

Which one sounds better in English depends on context.

Russian usually leaves that distinction to:

• context
• word order
• intonation
• what has already been mentioned

Yes. Russian word order is fairly flexible.

The sentence:

• Защитный уголок лежит на столе.

is a neutral way to say it.

You could also say:

• На столе лежит защитный уголок.

This often sounds more like:

• There is a protective corner piece on the table
• or it emphasizes where it is

Both are correct. The difference is mostly about emphasis and information structure, not basic grammar.

The stress is:

• защи́тный
• уголо́к
• лежи́т
• на столе́

So the sentence is pronounced roughly like:

• защи́тный уголо́к лежи́т на столе́

Stress is very important in Russian, because it is not always predictable and can affect both pronunciation and understanding.

Yes. Лежит is present tense, 3rd person singular.

Russian present tense here can correspond to either:

• lies
• is lying

in English, depending on context.

So:

• Защитный уголок лежит на столе can be translated as
  • The protective corner piece lies on the table
  • The protective corner piece is lying on the table

In natural English, is lying is usually more idiomatic here.

Yes. It is a completely normal Russian sentence.

Russian in the present tense usually does not use a verb equivalent to English am / is / are in simple statements like this.

So Russian says:

• Книга на столе. = The book is on the table.

But in your sentence there is already a main verb:

• лежит = lies / is lying

So nothing is missing. The sentence is fully complete as it stands.