Regimul alimentar este vegan.

Because regimul is the definite form of regim.

• regim = a regime / a diet
• regimul = the regime / the diet

Romanian usually puts the definite article at the end of the noun instead of using a separate word like the in English.

So:

• regim alimentar = a diet / dietary regime
• regimul alimentar = the diet / the dietary regime

In a standalone sentence like this, the definite form often sounds more natural if you are talking about a specific diet already understood from context.

Alimentar is an adjective meaning related to food / dietary.

It comes after the noun, which is the normal position for many Romanian adjectives:

• regim alimentar = dietary regime
• literally, something like regime dietary

This noun + adjective order is very common in Romanian.

Because in Romanian, adjectives often come after the noun by default.

So:

• regim alimentar not
• alimentar regim

English often puts adjectives before nouns, but Romanian commonly places them after. Some adjectives can come before the noun for style or emphasis, but here the normal order is regim alimentar.

Este is the 3rd person singular of a fi = to be.

• eu sunt = I am
• tu ești = you are
• el/ea este = he/she/it is

In standard Romanian, you normally do not omit the verb to be in a sentence like this. So:

• Regimul alimentar este vegan. = correct
• leaving out este would sound incomplete or ungrammatical in normal standard Romanian

Because regim is a neuter noun, and in the singular, neuter nouns usually behave like masculine for agreement.

So the predicate adjective stays in the masculine-looking singular form:

• regimul alimentar este vegan

Compare:

• dieta este vegană because dieta is feminine
• regimul este vegan because regim is neuter singular, which patterns like masculine in the singular

This is a very common thing in Romanian: neuter nouns are masculine in the singular and feminine in the plural for agreement purposes.

It is neuter.

That means:

• in the singular, it behaves like a masculine noun
• in the plural, it behaves like a feminine noun

So you get:

• singular: un regim vegan
• plural: două regimuri vegane

This mixed behavior is one of the special features of Romanian grammar.

A rough English-friendly pronunciation would be:

reh-ZHEE-mool ah-lee-men-TAR ES-te VEH-GAHN

A few notes:

• g in regimul sounds like the zh in measure
• e in este is clearly pronounced
• Romanian vowels are usually pronounced more clearly and consistently than in English
• vegan in Romanian is pronounced more like veh-GAHN, not like the common English VEE-gən

Yes, but it is a bit more formal or technical than some alternatives.

Common options include:

• regim alimentar = dietary regime / diet
• dietă = diet

So in everyday conversation, many people might also say:

• Dieta este vegană.

That sounds a little more direct and everyday.
Regimul alimentar este vegan is perfectly correct, but slightly more formal or descriptive.

Grammatically, they work in a similar way: both are adjectives and they agree with the noun.

Examples:

• regimul este vegan
• regimul este vegetarian
• dieta este vegană
• dieta este vegetariană

So the main thing to watch is agreement:

• with masculine/neuter singular nouns: vegan, vegetarian
• with feminine singular nouns: vegană, vegetariană

Yes. That means This diet is vegan.

• Acest = this for a masculine/neuter singular noun
• regim = neuter singular, so it takes acest

So:

• Acest regim alimentar este vegan. = This diet is vegan.

That version is very useful when you want to point to a specific diet more explicitly.

The plural would be:

Regimurile alimentare sunt vegane.

Breakdown:

• regimurile = the diets
• alimentare = plural form of the adjective
• sunt = are
• vegane = plural adjective form

This shows the neuter pattern clearly:

• singular: regimul alimentar este vegan
• plural: regimurile alimentare sunt vegane

In the plural, neuter nouns behave like feminine for agreement, so the adjective becomes vegane.