It's important to note that this word is masculine. If you're talking about a female friend, you'd use przyjaciółka (pronounced pri-YA-tsoon-ka).
Here are some other words related to friendship:
* kolega/koleżanka (pronounced koh-leh-gah/koh-leh-zhan-ka) - friend, colleague, classmate
* znajomy/znajoma (pronounced znah-yo-mee/znah-yo-ma) - acquaintance
* towarzysz (pronounced toh-var-rish) - companion, comrade
* bliskość (pronounced blis-kost) - closeness, intimacy