Mrtvé listy leží pod stromem.

They are:

• mrtvý = dead
• list = leaf
• ležet = to lie, to be lying
• pod = under
• strom = tree

So the sentence uses inflected forms of those base words:

• mrtvé from mrtvý
• listy from list
• leží from ležet
• stromem from strom

Because listy is a masculine inanimate plural noun, and the adjective has to agree with it.

In Czech, adjectives change their endings to match the noun’s:

• gender
• number
• case
• animacy

Here:

• listy = nominative plural
• masculine
• inanimate

So the correct adjective form is mrtvé.

Compare:

• mrtvé listy = dead leaves
• mrtví muži = dead men

The form mrtví is used with masculine animate plural nouns, not with things like leaves.

Because list is a masculine noun, and its nominative plural is listy.

So:

• list = leaf
• listy = leaves

This is a normal Czech plural pattern for many masculine nouns, though not all nouns form the plural in the same way.

You know from the case ending, not just from the word order.

In this sentence, listy is in the nominative plural, which is the case normally used for the subject. The adjective mrtvé also matches it in nominative plural.

So:

• mrtvé listy = the subject
• leží = the verb
• pod stromem = a location phrase

Czech relies much more on endings than English does.

Because after pod in this sentence, Czech uses the instrumental case to express a static location.

So:

• strom = tree
• stromem = by/with the tree in the instrumental form, here meaning under the tree

The full phrase pod stromem means under the tree or under a tree, depending on context.

This is a very important pattern.

• pod + instrumental = location, where something is
• pod + accusative = direction, where something is going

So here:

• Mrtvé listy leží pod stromem.
• The leaves are already there.
• So Czech uses instrumental: pod stromem

Compare with motion:

• Dám to pod strom. = I’ll put it under the tree.
• Here something moves to that place.
• So Czech uses accusative: pod strom

This location-vs-motion contrast is very common with Czech prepositions.

Because ležet is more specific than být.

• jsou pod stromem = they are under the tree
• leží pod stromem = they are lying under the tree

With things like leaves, clothes, books, or papers on the ground, Czech often prefers ležet because it describes their position more naturally.

So leží sounds more vivid and idiomatic here than just jsou.

It can be either.

In the present tense, ležet has the same form in 3rd person singular and 3rd person plural:

• On leží. = He/it is lying.
• Oni leží. = They are lying.

So you know the number from the subject:

• listy is plural
• therefore leží here means are lying

No. Czech word order is much more flexible than English word order.

The sentence:

• Mrtvé listy leží pod stromem.

is a neutral, straightforward way to say it.

But you could also say:

• Pod stromem leží mrtvé listy.

This still means the same thing, but it puts more focus on under the tree.

Because the endings show the grammatical roles, Czech can move words around more easily to change emphasis or style.

Because Czech does not have articles.

So stromem can mean:

• under the tree
• under a tree

Which one is meant depends on the context.

The same applies to listy:

• leaves
• the leaves

English requires articles, but Czech usually leaves that information implicit.

A simple guide is:

• Mrtvé: the r acts almost like a vowel here
• ž sounds like the sound in measure
• é and í are long vowels
• stress is usually on the first syllable of each Czech word

A rough pronunciation guide:

• MRT-vay LIS-ty LE-zhee pod STRO-mem

More exactly:

• mrtvé has a tricky Czech-style consonant cluster
• leží sounds roughly like le-zhee

The hardest word for many English speakers is mrtvé.

Yes, but it changes the nuance.

• listy = individual leaves
• listí = foliage, leaves as a mass

So:

• Mrtvé listy leží pod stromem. = Dead leaves are lying under the tree.
• Mrtvé listí leží pod stromem. = Dead foliage / dead leaves as a mass is lying under the tree.

In many situations both are possible, but listy makes you think more of separate leaves, while listí is more collective.