Learn Croatian: Mlijeko je bijelo.

The adjective bijelo (white) describes the noun mlijeko (milk). In Croatian, adjectives must match the gender of the noun they describe. Because mlijeko is a neuter noun, the adjective takes the neuter ending -o.

How can I tell that mlijeko is a neuter noun?

You can usually guess a Croatian noun's gender by looking at its last letter. Nouns ending in -o or -e are almost always neuter. Since mlijeko ends in -o, it is a neuter noun, which tells us we need the neuter form of the adjective.

If I look up "white" in a dictionary, will I find bijelo?

Usually, no. Dictionaries list adjectives in their basic masculine singular form. You would look up bijel (white). From there, you add the -a ending for feminine nouns or the -o ending for neuter nouns like mlijeko.

The English translation says "The milk", but there is no word for "the" in the Croatian sentence. Why?

Croatian does not have articles like "a", "an", or "the". The word mlijeko can mean either "milk" or "the milk". You have to figure out which one makes sense based on the context of the conversation.