Το υάλωμα καλύπτει τον πηλό.

Because Greek articles change according to gender, number, and case.

• υάλωμα is neuter singular, so its article here is το
• πηλός is masculine singular, and in this sentence it is the direct object, so it takes the accusative article τον

So the difference is not random: it reflects the grammar of each noun.

The subject is το υάλωμα and the object is τον πηλό.

A learner may expect word order alone to show this, as in English, but Greek also uses case forms:

• το υάλωμα is the thing doing the action
• τον πηλό is the thing receiving the action

So the sentence structure is:

• το υάλωμα = subject
• καλύπτει = verb
• τον πηλό = direct object

Because πηλό is the accusative singular form, and that is the form used for a direct object.

The dictionary form is ο πηλός, which is the nominative singular.
In this sentence, the noun is not the subject, so it changes:

• ο πηλός = nominative, subject form
• τον πηλό = accusative, direct-object form

This is a very common pattern with masculine nouns ending in -ός.

καλύπτει is the 3rd person singular present tense form of the verb καλύπτω.

So it means:

• he covers
• she covers
• it covers

In this sentence, it corresponds to it covers, because the subject is το υάλωμα.

Greek present tense can often mean either:

• a general present, like covers
• or an ongoing action, like is covering

The exact English translation depends on context.

Because Greek usually does not need an explicit subject pronoun when the verb form already shows the person and number.

The ending of καλύπτει already tells you it is 3rd person singular. And since the subject noun is already present as το υάλωμα, adding a separate it would be unnecessary.

This is normal in Greek. Greek is a language that often drops subject pronouns when they are clear from the verb.

Yes. Nouns ending in -μα are very often neuter in Greek.

So υάλωμα follows a very common pattern, like:

• το γράμμα
• το όνομα
• το πράγμα

That is why the article is το.

Also, with many neuter nouns, the nominative and accusative singular look the same. So το υάλωμα would have the same form whether it were subject or object.

Yes. Greek word order is more flexible than English word order.

The sentence Το υάλωμα καλύπτει τον πηλό is a neutral, straightforward way to say it. But Greek can also rearrange the words for emphasis, for example:

• Τον πηλό καλύπτει το υάλωμα

That would still mean the same basic thing, because the articles and noun forms show who is doing what.

So in Greek, case marking often matters more than word order.

A simple approximate pronunciation is:

to YA-lo-ma ka-LIP-ti ton pi-LO

A few helpful points:

• υά in υάλωμα is pronounced roughly like ya
• καλύπτει has the stress on -λύ-
• πηλό has the stress on the last syllable
• ει in καλύπτει sounds like ee

So the stress pattern is:

• υΆλωμα
• καΛΥπτει
• πηΛΟ

In a normal sentence like this, yes, they are usually expected.

Greek uses the definite article more often than English does. When referring to specific things, Greek normally keeps the article:

• το υάλωμα
• τον πηλό

Leaving the articles out would usually sound less natural, more like a label, heading, or very general statement.

The dictionary forms are:

• το υάλωμα for the noun υάλωμα
• καλύπτω for the verb
• ο πηλός for the noun πηλός

For nouns, Greek dictionaries normally list the nominative singular form.
For verbs, dictionaries normally list the 1st person singular present form, so καλύπτω rather than καλύπτει.

Because Greek spelling preserves distinctions that are not always heard in modern pronunciation.

In Modern Greek, several different spellings can represent the same i sound, including:

• ι
• η
• υ
• ει
• οι
• υι

So in καλύπτει, the ending -ει is spelled that way for grammatical and historical reasons, even though it is pronounced like i.

This is very normal in Greek spelling, and learners get used to it over time.