Learn Farsi: چای گرم است.

Farsi actually doesn't have a direct translation for the definite article 'the'. Since you are currently learning about using یک (yek) to say 'a' or 'an', you can think of it this way: if a noun doesn't have یک in front of it, it is usually understood as definite ('the tea') or it refers to the general concept of the noun. If we wanted to say 'A tea is warm', we would add the indefinite marker and say یک چای گرم است.

Why is the word است (is) at the very end?

In Farsi, verbs almost always go at the very end of the sentence. While English uses a Subject-Verb-Adjective order ('The tea is warm'), Farsi places the verb last. Literally, this sentence reads 'Tea warm is'.

The word for tea, چای, looks a lot like 'chai'. Are they pronounced the same?

Yes, it is pronounced exactly like the English word 'chai'! English actually adopted this word from other languages that share the same root. So if you already know what a chai latte is, you know the Farsi word for tea.