אי אפשר לעצב כלי חרס, אלא אם כן החימר במרכז האובניים.

אי אפשר is a fixed Hebrew expression meaning it is impossible, you can’t, or one cannot.

So אי אפשר לעצב... means something like:

• It’s impossible to shape...
• You can’t shape...

It is very common in Hebrew for general statements and rules.

Because אי אפשר is an impersonal expression. It does not need a stated subject.

Hebrew often uses this structure when English would use a general you:

• אי אפשר לדעת = You can’t know
• אי אפשר להיכנס = You can’t enter

So this sentence is stating a general fact, not talking about one specific person.

After אי אפשר, Hebrew normally uses ל־ + infinitive.

So:

• אי אפשר להבין = It’s impossible to understand
• אי אפשר לעשות = It’s impossible to do
• אי אפשר לעצב = It’s impossible to shape

This is the normal pattern.

Here לעצב means to shape, to form, or to mold.

In other contexts, the same verb can also mean to design. For example, it can refer to designing a room, a logo, or a piece of clothing. But with clay and pottery, the meaning is clearly shape / mold.

This is a very good question, because both words are related to clay and pottery, but they are not the same.

• חימר = clay as a material
• חרס = earthenware / pottery / fired clay in many contexts

So in this sentence:

• החימר refers to the raw clay being worked on the wheel
• כלי חרס refers to the finished type of object: an earthenware vessel or pottery item

In other words, חימר is the material, while חרס is the pottery object or pottery substance.

כלי חרס is a construct phrase.

It is built from:

• כלי = vessel / utensil / container
• חרס = earthenware / clay pottery

Together, it means something like:

• an earthenware vessel
• a clay vessel
• pottery ware

The exact English wording depends on context.

Without vowel marks, כלי can be ambiguous in writing.

It may represent:

• כְּלִי = singular, a vessel
• כְּלֵי = plural construct, vessels of

So written Hebrew does not always show the difference clearly.

In this sentence, readers usually understand it generically, something like a clay vessel or pottery. The context tells you what makes most sense.

אלא אם כן is a fixed expression meaning unless.

It is best learned as one chunk.

A rough breakdown is:

• אלא = except
• אם = if
• כן = so / thus

But in normal reading, you should not translate each word separately. Just recognize אלא אם כן as the standard way to say unless.

Example:

• לא אבוא, אלא אם כן תבוא גם אתה = I won’t come unless you come too

Because Hebrew usually leaves out the verb to be in the present tense.

So:

• החימר במרכז האובניים = the clay is in the center of the wheel
• הספר על השולחן = the book is on the table

But in past or future, Hebrew does use a form of to be:

• החימר היה במרכז = the clay was in the center
• החימר יהיה במרכז = the clay will be in the center

Because the sentence is talking about a specific lump of clay in the situation being described.

So החימר means the clay—the clay on the wheel, the clay being used.

If you said just חימר, it would sound more like clay as a substance in general, not the specific clay involved here.

Because Hebrew often prefers a construct phrase instead of using של.

So:

• מרכז האובניים = the center of the potter’s wheel

This is more compact and more natural here than המרכז של האובניים.

Both patterns exist in Hebrew, but the construct form is very common, especially in concise written language.

Because מרכז האובניים is a construct phrase.

In Hebrew construct phrases, the first noun usually does not take ה־. The whole phrase becomes definite because the second noun is definite.

So:

• מרכז אובניים = center of a potter’s wheel
• מרכז האובניים = the center of the potter’s wheel

This is the same idea as:

• בית ספר = a school
• בית הספר = the school

אובניים means potter’s wheel.

It ends in ־יים, which often looks like a dual or plural ending. Some Hebrew nouns have this kind of historical form even when they refer to a single object in English.

So you should learn אובניים as a single vocabulary item meaning potter’s wheel, not assume it must mean two wheels.

Not in the same way.

לא יכול means cannot for a specific subject, so it must agree with that subject:

• אני לא יכול = I can’t
• היא לא יכולה = she can’t

But אי אפשר is impersonal and general:

• אי אפשר לעצב... = You can’t / It’s impossible to shape...

So אי אפשר is the natural choice when stating a general rule or condition.