Learn Italian: Mio fratello è un perfezionista, ma io sono un realista. - My brother is a perfectionist, but I am a realist.

Nouns formed with the suffix -ista (indicating professions, followers, or personality types) always end in -a in the singular, regardless of gender. You can tell they are masculine here because of the masculine article un. If the speaker were female, it would be una realista.

If I wanted to talk about my brothers in the plural, how do these -ista nouns change?

This is where their gender becomes visible in the ending! Masculine -ista nouns change to -isti in the plural (so, i miei fratelli sono perfezionisti). Feminine -ista nouns change to -iste (le mie sorelle sono perfezioniste).

What base words were used to form perfezionista and realista?

The suffix -ista is very flexible. Perfezionista is built from the noun perfezione (perfection), dropping the final vowel to add the suffix. Realista is built from the adjective reale (real). This shows how -ista can attach to different parts of speech to describe someone's traits or beliefs.

Why is it Mio fratello instead of Il mio fratello?