Катушка лежит на полу.

Russian often distinguishes how something is positioned.

• лежать / лежит = to be lying
• стоять / стоит = to be standing
• сидеть / сидит = to be sitting

So Катушка лежит на полу means the spool/coil is lying on the floor, not standing upright.

For many objects, Russian naturally chooses one of these verbs based on the object's position. English often just says is.

In the present tense, Russian usually does not use a separate verb meaning is / am / are in ordinary sentences like this.

So:

• Катушка лежит на полу = The spool is lying on the floor

The idea of is is built into the sentence structure, and лежит already gives the main verbal meaning.

Лежит is the 3rd person singular present tense form of лежать.

That means it is used with:

• he
• she
• it
• singular nouns like катушка

So:

• катушка лежит = the spool lies / is lying

Because катушка is singular, the verb is singular too.

Катушка is a feminine noun, and one big clue is that it ends in -а.

This is a very common pattern in Russian:

• nouns ending in -а / -я are often feminine

So dictionaries list it as feminine, and that affects agreement in other contexts, for example with adjectives or past tense verbs.

Because this sentence describes location, not movement.

Russian uses different cases depending on whether you mean:

• where something is → Prepositional case
• where something is going → often Accusative case

So:

• Катушка лежит на полу = the spool is on the floor
• Положить катушку на пол = to put the spool onto the floor

Here the spool is already there, so на takes the Prepositional form.

Пол means floor, and in this sentence it is in the Prepositional singular after на to show location.

Its forms are:

• пол = nominative
• пола = genitive
• полу = prepositional/dative form in this expression

So:

• на полу = on the floor

This is a very common phrase, and learners usually just memorize на полу as a set expression.

The basic order here is:

• Катушка = subject
• лежит = verb
• на полу = location

So it is a normal, neutral sentence.

But Russian word order is flexible. You could also say:

• На полу лежит катушка.

That still means the same thing, but it may sound like you are emphasizing the location first: On the floor there is a spool / A spool is lying on the floor.

The stress is:

• катУшка
• лежИт
• на полу́

So the full sentence is pronounced roughly like:

• ka-TOOSH-ka lye-ZHEET na pa-LOO

The stressed syllables are important in Russian, because stress is not always predictable.

Yes. In English, Russian present tense verbs like лежит can often be translated in more than one natural way:

• The spool lies on the floor.
• The spool is lying on the floor.

In normal English, is lying is usually more natural. But both reflect the same Russian form here.

Yes. Катушка can mean things like:

• a spool
• a bobbin
• a coil

The exact English word depends on context. Russian often uses one noun where English might choose among several more specific words.

So even though the grammar stays the same, the best translation of катушка can vary.