כלי חרס שבירים עלולים להישבר.

Because the rest of the sentence shows plural agreement.

In unpointed Hebrew, כלי can be:

• kli = a single vessel / utensil
• klei = the construct form of the plural כלים, meaning vessels of ...

Here, both שבירים and עלולים are masculine plural, so כלי must be read as klei, not kli.

So כלי חרס here means earthenware vessels, not an earthenware vessel.

Yes. It is a classic Hebrew construct chain.

• כלי = vessels of ...
• חרס = earthenware / clay / pottery

So literally it means vessels of earthenware.

English often prefers a different structure, such as:

• earthenware vessels
• clay vessels
• pottery vessels

This is very common in Hebrew: one noun is followed by another noun that tells you the material, type, owner, purpose, and so on.

Because in present-tense Hebrew, the verb to be is usually omitted.

So:

• כלי חרס שבירים literally looks like earthenware vessels fragile
• but it means earthenware vessels are fragile

This is normal Hebrew grammar.

If you wanted past or future, Hebrew would usually use forms of היה:

• כלי חרס היו שבירים = earthenware vessels were fragile
• כלי חרס יהיו שבירים = earthenware vessels will be fragile

Because Hebrew adjectives must agree with the noun they describe in gender and number.

Here the noun phrase is understood as masculine plural, so the adjective is also masculine plural:

• שביר = masculine singular
• שבירה = feminine singular
• שבירים = masculine plural
• שבירות = feminine plural

So שבירים matches כלי חרס.

שביר means fragile, breakable, or brittle, depending on context.

In this sentence, fragile is usually the most natural English choice. It describes a quality of the vessels: they break easily.

So שבירים is not an action. It is a description.

עלולים is the masculine plural form of עלול, which means something like:

• likely to
• liable to
• prone to
• at risk of

It is commonly followed by an infinitive with ל־.

So:

• עלולים להישבר = likely to break / liable to break

Important: עלול behaves more like an adjective than like an English modal verb. It changes form to match the subject:

• עלול = masculine singular
• עלולה = feminine singular
• עלולים = masculine plural
• עלולות = feminine plural

להישבר means to break in the sense of to get broken or to be broken.

That is why it fits here: the vessels are the ones undergoing the breaking.

Compare:

• לשבור = to break something
• להישבר = to break / to get broken

For example:

• הילד עלול לשבור את הכלי = the child may break the vessel
• הכלי עלול להישבר = the vessel may break

So in your sentence, להישבר is the correct choice because the subject is not doing the breaking; it is receiving it.

A little, but not in a bad way.

The two parts are related, but they do different jobs:

• שבירים describes a general property: fragile
• עלולים להישבר describes a possible event: may break

So the sentence is roughly saying:

• they are fragile
• therefore they may break

This kind of overlap is normal. English can do something similar too, as in Fragile items can easily break.

Because the sentence follows normal Hebrew patterns.

Its structure is basically:

• כלי חרס = earthenware vessels
• שבירים = fragile
• עלולים להישבר = are likely to break

So the order is:

noun phrase + adjective + expression with infinitive

A very literal breakdown would be:

earthenware vessels, fragile, are liable to break

That sounds awkward in English, but it is natural in Hebrew.

You would change the agreeing words to singular:

כלי חרס שביר עלול להישבר.

That means An earthenware vessel is fragile and may break or A clay vessel may break easily.

Notice the agreement:

• שביר instead of שבירים
• עלול instead of עלולים

In a construct chain, definiteness is usually shown on the second noun.

So a definite version would be something like:

כלי החרס שבירים ועלולים להישבר.

That means The earthenware vessels are fragile and may break.

Notice that the predicate adjectives do not take ה־ here:

• כלי החרס = the earthenware vessels
• שבירים = fragile
• עלולים להישבר = likely to break

A common pronunciation would be:

klei ḥeres shvirim alulim lehishaver

A few notes:

• כלי here is klei, not kli
• ח in חרס is a throaty sound, not a regular English h
• להישבר is stressed at the end: lehishavER

If you read כלי as kli, the sentence will sound wrong because the grammar around it is plural.