במקרר יש ביצים, גבינה ומלפפון אחד.

Because Hebrew often attaches short prepositions directly to the next word.

• ב־ = in
• מקרר = refrigerator / fridge

So במקרר is literally in + refrigerator.

This is very normal in Hebrew. You will also see the same thing with other short prepositions, such as ל־ (to/for) and כ־ (as/like).

When ב־ combines with ה־ (the), Hebrew usually merges them.

So underlyingly, this is:

• ב + ה + מקרר

And in normal writing it becomes:

• במקרר

In pronunciation, the definite form is typically ba-mekarer, even though the ה is no longer written as a separate letter.

In unpointed Hebrew spelling, במקרר can be ambiguous.

It can represent either:

• in the fridge
• in a fridge

Usually, context tells you which one is meant. In everyday situations, with something like a household fridge, people often understand it as in the fridge.

יש means there is or there are.

It is used to express existence:

• יש ביצים = there are eggs
• יש גבינה = there is cheese

So in this sentence, יש introduces the things that are present in the fridge.

Because Hebrew normally does not use a present-tense form of to be the way English does.

In an existence sentence, Hebrew uses יש instead.

Compare:

• במקרר יש ביצים = There are eggs in the fridge
• הביצים במקרר = The eggs are in the fridge

In the second sentence, there is no separate present-tense word for are.

Because יש does not change for singular or plural.

English distinguishes:

• there is
• there are

Hebrew usually just uses יש for both:

• יש מלפפון אחד = there is one cucumber
• יש ביצים = there are eggs

So יש stays the same no matter how many things follow.

In Modern Hebrew, when אחד/אחת means the number one, it usually comes after the noun.

So:

• מלפפון אחד = one cucumber
• ביצה אחת = one egg

This is different from English, where one usually comes before the noun.

Because מלפפון is a masculine noun, and אחד is the masculine form of one.

• masculine: אחד
• feminine: אחת

So:

• מלפפון אחד = one cucumber
• ביצה אחת = one egg

The number has to match the grammatical gender of the noun.

Because Hebrew has no indefinite article.

English has:

• a cucumber
• an egg

Hebrew usually just uses the noun by itself for that idea.

So מלפפון can mean a cucumber depending on context. In this sentence, אחד does not mean a; it specifically means one.

Because גבינה is being used as a mass noun, like English cheese.

You normally say:

• יש גבינה = there is cheese

not because there is exactly one cheese, but because it is an uncounted substance.

By contrast, ביצים are individual countable items, so the plural is used naturally:

• יש ביצים = there are eggs

Yes. Hebrew has some flexibility here.

במקרר יש ביצים, גבינה ומלפפון אחד is very natural because it starts with the location: in the fridge.

You could also say:

• יש במקרר ביצים, גבינה ומלפפון אחד

The meaning is basically the same, but the emphasis shifts a little. Starting with במקרר helps set the scene first.