Ο λασπωτήρας είναι καθαρός.

Ο is the masculine singular form of the definite article, equivalent to the.

It is capitalized here only because it is the first word of the sentence. In the middle of a sentence, it would be written ο.

Because λασπωτήρας is a masculine noun, Greek uses ο with it. Compare:

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

You can tell from two clues:

1. It takes the article ο, which is masculine nominative singular.
2. Its ending -ας is a very common masculine noun ending in Greek.

So ο λασπωτήρας is grammatically masculine singular.

This is a grammatical category, not a statement about biological sex. In Greek, all nouns have grammatical gender.

It is nominative singular masculine.

Why?

• nominative: it is the subject of the sentence
• singular: it refers to one thing
• masculine: shown by both the article ο and the noun pattern

So ο λασπωτήρας is the subject, meaning it is the thing being described.

Because Greek adjectives must agree with the noun they describe in:

• gender
• number
• often case

Since λασπωτήρας is masculine singular nominative, the adjective must also be masculine singular nominative:

• καθαρός = masculine
• καθαρή = feminine
• καθαρό = neuter

So καθαρός is the correct form here.

Because after είναι in a sentence like this, the adjective is a predicate adjective. In Greek, predicate adjectives normally agree with the subject and appear in the nominative.

So in:

Ο λασπωτήρας είναι καθαρός

both λασπωτήρας and καθαρός are nominative singular masculine.

This is similar to English The mudguard is clean, where clean describes the subject rather than acting as an object.

Here είναι means is.

It is the present-tense form of the verb to be. In this sentence, it links the subject ο λασπωτήρας with the description καθαρός.

So the structure is:

• ο λασπωτήρας = subject
• είναι = linking verb
• καθαρός = description of the subject

A useful thing to know: είναι can also mean are with they, depending on the subject. The form is the same.

In normal standard Greek, yes.

If you want to say that something is something or is in a certain state, you usually use είναι:

• Ο λασπωτήρας είναι καθαρός.

You may sometimes see omission of the verb in headlines, labels, notes, or very informal elliptical speech, but that is not the normal full-sentence pattern learners should copy.

A rough English-style pronunciation is:

o las-po-TEE-ras EE-ne ka-tha-ROS

A few details:

• λασπωτήρας → stress on τή
• είναι → stress on the first syllable: EE-ne
• καθαρός → stress on the last syllable: ρός
• θ in καθαρός sounds like th in think
• ρ is a Greek r, usually tapped or lightly rolled
• αι in είναι is pronounced like e in Modern Greek
• ω and ο are both pronounced o in Modern Greek

The accent marks show which syllable is stressed.

In this sentence:

• λασπωτήρας → stress on τή
• είναι → stress on εί
• καθαρός → stress on ρός

Modern Greek spelling uses one main accent mark, called the τόνος. It is very important because stress is part of correct pronunciation.

Notice that ο has no accent. That is normal: it is a one-syllable article and is not stressed here.

This is the most neutral, straightforward order:

Ο λασπωτήρας είναι καθαρός.

Greek word order is more flexible than English, so other orders are possible for emphasis, such as putting extra focus on clean. But for a learner, the sentence as given is the safest and most natural pattern to use.

So yes, word order can change, but the original version is the standard one to learn first.

They do not mean the same thing grammatically.

• Ο λασπωτήρας είναι καθαρός = The mudguard is clean
• Ο καθαρός λασπωτήρας = The clean mudguard

In the first sentence, καθαρός is a predicate adjective after είναι. It tells you the state of the mudguard.

In the second phrase, καθαρός comes directly before the noun and works attributively, like an ordinary adjective inside a noun phrase.

So:

• X is clean → Ο λασπωτήρας είναι καθαρός
• the clean X → Ο καθαρός λασπωτήρας