Questions & Answers about Compro media docena de huevos.
Why is it media instead of medio?
Media translates to half, and it acts like an adjective here, changing its ending to match the noun it describes. Because docena (dozen) is a feminine noun, you must use media.
Why isn't there a word for 'a' in front of media docena?
Why do we need the word de before huevos?
Can compro also mean 'I am buying' in this context?
Yes! In Spanish, the simple present tense like compro is frequently used to express what you are doing right now (I am buying) as well as general habits (I buy). You do not always need to use the present continuous form.