Learn Finnish: Otan maitoa jääkaapista. - I take some milk from the fridge.

To say from or out of the fridge, we add the elative ending -sta. Also, because adding this ending closes the last syllable, the double pp in jääkaappi drops to a single p, making it jääkaapista.

Why is the word for milk maitoa instead of just maito?

Milk is a liquid, which means it is an uncountable mass noun. When you take an undefined amount of an uncountable thing, it goes into the partitive case. Adding the -a ending to maito gives us maitoa to mean some milk.

Why does the verb ottaa (to take) become otan here with only one t?

This is due to consonant gradation. When we add the -n ending to say I take, the syllable becomes closed. This weakens the strong double tt in the basic word ottaa into a single t.

What are the parts that make up the word jääkaappi?

It is a compound word made of jää meaning ice and kaappi meaning cupboard or cabinet. So, a fridge is literally an ice cupboard!