Ovo su grickalice.

Because grickalice is plural, and the verb biti (to be) agrees with that plural noun here.

• je = is
• su = are

So:

• Ovo je grickalica. = This is a snack.
• Ovo su grickalice. = These are snacks.

Even though ovo looks singular, in this kind of identifying sentence the verb agrees with the noun being identified: grickalice.

Ovo is a demonstrative pronoun meaning something like this or, in English translation, sometimes these.

In sentences like this, Croatian often uses ovo as a general pointing/identifying word:

• Ovo je knjiga. = This is a book.
• Ovo su knjige. = These are books.

So ovo does not always map neatly to just one English word. In this sentence, it helps introduce or identify what you are pointing at.

This is a very common question.

Croatian often uses neuter singular ovo in identifying sentences, even when the noun that follows is plural or has a different gender:

• Ovo su grickalice.
• Ovo su moja djeca.
• Ovo su knjige.

Here, ovo works like this/these here in a general pointing sense.

You can also see ove in other structures, but it is not the same thing:

• ove grickalice = these snacks
  (the demonstrative directly modifies the noun, so it agrees with it: feminine plural)

So:

• Ovo su grickalice. = identifying what something is
• Ove grickalice = these snacks

It can correspond to either one in English, depending on the sentence.

In Ovo su grickalice, English naturally says these are snacks, even though Croatian still uses ovo.

So the best way to think about it is:

• ovo = a pointing word used for this / these
• the rest of the sentence tells you whether English will use singular or plural

Grickalice is the nominative plural form of grickalica.

• singular: grickalica
• plural: grickalice

It is a feminine noun.

That is why, when it agrees with adjectives or demonstratives directly, you get feminine plural forms such as:

• ove grickalice = these snacks
• dobre grickalice = good snacks

Because this is an equational/identifying sentence with the verb to be.

In sentences like X is Y, Croatian normally uses the nominative for the noun that identifies something:

• Ovo je knjiga.
• Ovo su grickalice.

So grickalice is not an object here. It is the noun that tells you what ovo is.

Because su is a clitic in Croatian.

Clitics are short words that usually go in the second position of the clause. In a simple sentence like this, that means su comes after the first word:

• Ovo su grickalice.

This is the normal pattern in Croatian. English speakers often want to place the verb more freely, but Croatian clitics have stricter placement rules.

The neutral, standard order is:

• Ovo su grickalice.

Other orders may be possible in special contexts, but they usually sound marked, contrastive, or less natural for a basic statement.

For a learner, the safest choice is to keep:

• Ovo
  • su
    • grickalice

That is the most natural way to say it in an ordinary situation.

Because Croatian does not have articles like English.

So grickalice can mean:

• snacks
• the snacks

The exact meaning depends on context.

That is very normal in Croatian. You do not need to add a separate word for a, an, or the.

No, not in standard Croatian present-tense sentences like this.

You normally must include the present form of biti:

• Ovo su grickalice. ✓
• Ovo grickalice. ✗

So unlike some Slavic languages, Croatian keeps the present-tense is/are form here.