תני לי כוס נקייה, כי הכוס הזאת לא טובה.

תני is the imperative form used when speaking to one female.

• תן = give! (to one male)
• תני = give! (to one female)
• תנו = give! (to more than one person)

So this sentence is being said to a woman or girl.

לי means to me.

It is made from:

• ל־ = to
• י = me

In Hebrew, short prepositions like ל (to), ב (in), and כ (as/like) are often attached directly to the word or pronoun that follows. So instead of writing two separate words, Hebrew combines them:

• לי = to me
• לך = to you
• לו = to him
• לה = to her

So תני לי literally means give to me, which is how Hebrew normally says give me.

Hebrew usually has no separate indefinite article. English says a cup or a clean cup, but Hebrew simply says:

• כוס = cup / a cup
• כוס נקייה = clean cup / a clean cup

If Hebrew wants to make something definite, it uses ה־:

• כוס = a cup / cup
• הכוס = the cup

So כוס נקייה means a clean cup, even though there is no separate word for a.

In Hebrew, adjectives normally come after the noun.

So:

• כוס נקייה = a clean cup
• literally: cup clean

This is the normal Hebrew order. A few examples:

• ילד טוב = a good boy
• מכונית גדולה = a big car
• ספר מעניין = an interesting book

So כוס נקייה is exactly what you should expect in Hebrew word order.

Because כוס is a feminine noun in Hebrew.

Adjectives in Hebrew must agree with the noun in:

• gender
• number
• definiteness

Since כוס is feminine singular, the adjective also has to be feminine singular:

• masculine singular: נקי
• feminine singular: נקייה

So:

• כוס נקייה = a clean cup

Even though the word כוס does not end in ־ה, it is still feminine. Hebrew noun gender is something you often just have to learn with each noun.

In Hebrew, when you say this/that with a noun, the noun is usually definite, so it normally takes ה־.

That means Hebrew says:

• הכוס הזאת = this cup
• literally: the-cup this

This is different from English. English says this cup, but Hebrew usually uses the + noun + this/that.

A few more examples:

• הספר הזה = this book
• הילדה הזאת = this girl
• הבית ההוא = that house

So הכוס הזאת is the normal way to say this cup.

Because כוס is feminine.

Hebrew demonstratives like this also agree with the noun's gender:

• הזה = this (masculine singular)
• הזאת = this (feminine singular)

So:

• הספר הזה = this book
• הכוס הזאת = this cup

Since כוס is feminine, the correct form is הזאת.

Again, this is because כוס is feminine.

The adjective טוב (good) must agree with כוס, so it becomes feminine singular:

• masculine singular: טוב
• feminine singular: טובה

So:

• הכוס הזאת לא טובה = this cup is not good

Even though English uses good for everything, Hebrew changes the adjective to match the noun.

In present-tense Hebrew, the verb to be is usually not expressed.

So Hebrew says:

• הכוס הזאת לא טובה
• literally: this cup not good

But it means:

• This cup is not good

This is completely normal in Hebrew. In the present tense, you usually do not say a word for is/am/are.

Compare:

• אני עייף = I am tired
• היא שמחה = she is happy
• הם בבית = they are at home

No separate word for am/is/are appears in these sentences.

כי means because in this sentence.

So the structure is:

• תני לי כוס נקייה = Give me a clean cup
• כי הכוס הזאת לא טובה = because this cup is not good

Hebrew כי is very common and can have different meanings in different contexts, but in a sentence like this, because is the natural meaning.

Hebrew uses את before a definite direct object, not before an indefinite one.

Here, כוס נקייה means a clean cup, which is indefinite, so there is no את.

Compare:

• תני לי כוס נקייה = Give me a clean cup
• תני לי את הכוס הנקייה = Give me the clean cup

So the absence of את helps show that the speaker wants any clean cup, not one specific already-known cup.

Only the imperative would change:

• to a woman: תני לי כוס נקייה, כי הכוס הזאת לא טובה.
• to a man: תן לי כוס נקייה, כי הכוס הזאת לא טובה.

Everything else stays the same, because the rest of the sentence is about the cup, not about the person being addressed.

A simple pronunciation guide is:

Tni li kos nekiya, ki ha-kos ha-zot lo tova.

A few notes:

• תני = tni
• כוס = kos
• נקייה = nekiya
• הכוס = ha-kos
• הזאת = ha-zot
• לא = lo
• טובה = tova

In natural speech, the sentence flows smoothly, and the stress usually falls near the end of words like נקייה and טובה.