Το τραπεζομάντιλο ήταν λευκό, αλλά το πιατάκι είχε έναν μικρό λεκέ από σάλτσα.

Because both nouns are neuter singular nouns in Greek.

Greek nouns have grammatical gender, and the article must agree with the noun:

• ο for masculine
• η for feminine
• το for neuter

So:

• το τραπεζομάντιλο
• το πιατάκι

Both are neuter, so both take το.

Πιατάκι is a diminutive form of πιάτο.

The ending -άκι often means:

• small
• sometimes cute
• sometimes simply a more natural everyday word for a smaller version of something

So πιατάκι can mean:

• small plate
• saucer
• little dish

In context, it often sounds more natural than just mechanically translating it as tiny plate.

Because the adjective must agree with the noun it describes.

Here, λευκό describes τραπεζομάντιλο, which is neuter singular, so the adjective also has to be neuter singular:

• masculine: λευκός
• feminine: λευκή
• neuter: λευκό

So:

• το τραπεζομάντιλο ήταν λευκό

These are past-tense forms:

• ήταν = was
• είχε = had

More specifically, both are in the imperfect. In a sentence like this, Greek often uses the imperfect to describe a situation or background in the past:

• the tablecloth was white
• the saucer had a small stain

This is very natural when describing what something looked like or what condition it was in.

Because this phrase is the direct object of είχε.

The noun λεκές is a masculine noun. Since it is the object, it appears in the accusative singular:

• nominative: ένας μικρός λεκές
• accusative: έναν μικρό λεκέ

So after είχε, you need the accusative form:

• είχε έναν μικρό λεκέ

The dictionary form is ο λεκές.

But in the accusative singular, many masculine nouns lose the final -ς:

• ο λεκές → τον λεκέ
• ένας λεκές → έναν λεκέ

So in this sentence, λεκέ is not a different word. It is just the correct case form after είχε.

Here από means something like from or caused by.

So λεκές από σάλτσα means:

• a stain from sauce
• a stain caused by sauce

It shows the source of the stain.

Greek often uses από this way with stains, marks, smells, and similar things.

Because σάλτσα is being mentioned in a general, indefinite way.

So από σάλτσα means:

• from sauce
• from some sauce

If you were talking about a specific sauce already known in the conversation, you could say:

• από τη σάλτσα

Without the article, it sounds more general and natural here.

In Modern Greek, από is followed by the accusative.

However, with many feminine nouns like σάλτσα, the nominative singular and accusative singular look the same:

• nominative: η σάλτσα
• accusative: τη σάλτσα

Without the article, you just see σάλτσα, so there is no visible change in the noun itself.

Greek word order is more flexible than English word order.

The sentence as written is very natural and neutral:

• Το τραπεζομάντιλο ήταν λευκό, αλλά το πιατάκι είχε έναν μικρό λεκέ από σάλτσα.

But Greek could move parts around for emphasis. For example, a speaker might emphasize the stain or the sauce in a different context.

Even when word order changes, the articles and endings still show how the words function in the sentence. That is one reason Greek can be more flexible than English.