Learn Farsi: اسفند ماهِ زمستان است.

In English, we put the descriptive word first: 'winter month'. Farsi builds this differently by linking the two nouns with the ezafe sound (-e). It literally translates to 'month of winter' (mah-e zemestan).

The English translation says 'a winter month', but there is no word for 'a' (یک) in the Farsi sentence. Why?

When making general statements classifying what something is, Farsi often skips the indefinite article. Because you are just categorizing Esfand as a type of month rather than counting it, you don't need یک or the suffix -ی here.

Is اسفند just the Farsi word for a specific English month?

اسفند (Esfand) is actually the twelfth and final month of the official solar calendar used in Iran. It roughly corresponds to February 20th through March 20th, which is why it is firmly a winter (زمستان) month just before the Persian New Year in spring.

Why does the verb است come at the very end instead of right after اسفند?

Farsi is a Subject-Object-Verb language, meaning the verb almost always anchors the end of the sentence. While English follows a Subject-Verb-Object pattern ('Esfand is a winter month'), Farsi puts the 'is' at the end: 'Esfand [a winter month] is'.