Learn Hardcore Russian: На стуле лежит пара джинсов.

In Russian, verbs like лежать (to lie), стоять (to stand), сидеть (to sit), висеть (to hang) are very commonly used to describe where an object is.

лежит literally means “is lying” and describes the position of the jeans.
На стуле лежит пара джинсов = “A pair of jeans is lying on the chair.”

You could say:

На стуле находится пара джинсов. – grammatically correct, but more formal/technical and less natural here.
You would NOT use есть here. есть is for basic existence (“there is/are”) and usually appears as у меня есть…, здесь есть…. With a specific object on a specific surface, Russians strongly prefer лежит/стоит/висит/сидит.

Why is the verb лежит (singular) and not лежат (plural), when jeans in English is plural?

The verb agrees with the grammatical subject, which is пара (“pair”), not джинсов.

пара is singular feminine.
So the verb must be 3rd person singular: лежит.

Structure:

На стуле – location (on the chair)
лежит – 3rd singular verb
пара джинсов – subject (“a pair of jeans”)

If you drop пара and make джинсы the subject, the verb becomes plural:

На стуле лежат джинсы. – “Jeans are lying on the chair.”

What case is джинсов, and why is it used here?

джинсов is genitive plural of джинсы.

After пара (“a pair”), Russian normally uses the genitive plural:

пара джинсов – a pair of jeans
пара ботинок – a pair of shoes
пара носков – a pair of socks

So the pattern is:

пара + genitive plural of the thing that comes in a pair.

Why is it пара джинсов and not just пара джинсы?

Because джинсы is a plural-only noun (pluralia tantum).

The base form is plural: джинсы (“jeans”).
Its genitive plural is джинсов.
After пара, you need genitive plural, so: пара джинсов.

пара джинсы would be ungrammatical in standard Russian.

Is пара джинсов the usual way to say “a pair of jeans,” or can I just say джинсы?

Both are used, but a bit differently:

джинсы – just “jeans” (one pair, in most everyday contexts).
- На стуле лежат джинсы. – Most natural neutral sentence.
пара джинсов – explicitly “a pair of jeans.”
- Used when you want to stress one pair among other clothes, or count pairs:
  - У меня есть две пары джинсов. – I have two pairs of jeans.

So пара джинсов is correct and clear, but in daily speech people often simply say джинсы when talking about one pair.

What case is на стуле, and why do we use it with на here?

на стуле is prepositional singular of стул.

Nominative: стул (chair)
Prepositional: на стуле, о стуле

With на:

где? (where?) → на
- prepositional: на стуле – on the chair
куда? (onto where?) → на
- accusative: на стул – onto the chair

In this sentence we are talking about location (where the jeans are), so we use на стуле.

Why is it на стуле and not в стуле?

на means “on (a surface)” and в means “in (inside something).”

A chair is seen as a surface the jeans lie on, not something they are inside:

На стуле лежит пара джинсов. – The jeans are on top of the chair.
В стуле would mean “inside the chair” (physically inside its structure), which is not what we mean here.

So for objects placed on flat furniture surfaces (chair, table, shelf), Russian normally uses на.

Can I change the word order to Пара джинсов лежит на стуле? Does it change the meaning?

Yes, you can say:

Пара джинсов лежит на стуле.

The basic meaning is the same. The difference is in emphasis:

На стуле лежит пара джинсов. – Slight focus on the place: “On the chair, there’s a pair of jeans.” (Maybe someone asked “What’s on the chair?”)
Пара джинсов лежит на стуле. – Slight focus on the object: “The pair of jeans is on the chair.” (Maybe someone asked “Where are the jeans?”)

Both are natural, grammatical sentences.

Can I omit лежит and say just На стуле пара джинсов?

You can say На стуле пара джинсов, but the meaning shifts:

На стуле лежит пара джинсов. – explicitly says the jeans are lying on the chair.
На стуле пара джинсов. – just states existence/location: “On the chair (there is) a pair of jeans.”

In the second sentence, the verb быть (“to be”) is omitted (as it usually is in the present tense), but лежать is not implied. It’s more like: “On the chair – a pair of jeans.” So use лежит if you want to keep the idea of the jeans lying there.

What exactly does лежит express here? Is it a particular tense or aspect?

лежит is:

present tense
3rd person singular
imperfective aspect
of the verb лежать (“to lie, be lying”).

So it describes a current, ongoing state: “is lying (now / generally).” There is no notion of completed action; it just states how the jeans are positioned at this moment.

Why use лежит and not стоит or висит for clothes?

Russian is quite strict about position verbs:

лежать – for things lying flat or resting on a surface (books on a table, clothes on a chair/bed, etc.).
стоять – for things that “stand” upright (bottles, furniture, TVs, etc.).
висеть – for things hanging (clothes on a hanger, lamps, pictures on a wall).

Jeans placed on a chair are seen as lying, not standing or hanging, so:

На стуле лежит пара джинсов.
But: На вешалке висит пара джинсов. – A pair of jeans is hanging on the hanger.

How would I say simply “Jeans are lying on the chair” without пара?

You would say:

На стуле лежат джинсы.

Here:

джинсы – plural subject
Verb agrees in plural: лежат

Compare:

На стуле лежит пара джинсов. – A pair of jeans is lying on the chair.
На стуле лежат джинсы. – Jeans are lying on the chair. (Normally understood as one pair, unless context says otherwise.)

How do you pronounce the words стуле, лежит, пара, джинсов?

Approximate pronunciation (stressed syllable in CAPS):

стуле – STU-lye (СТУ́-ле)
лежит – lee-ZHEET (ле-ЖИ́Т)
пара – PAH-ra (ПА́-ра)
джинсов – DJIN-sof (ДЖИ́Н-сов)

Put together:

На стуле лежит пара джинсов. ≈ Na STOO-lye lee-ZHEET PAH-ra DJIN-sof.