What it means
مثلث (mosallas) means “triangle,” a shape with three sides and three angles. It is an Arabic loanword built on the root ث-ل-ث, which carries the meaning of “three,” so the word literally means “tripled” or “made threefold.” Persian uses this word across all contexts, from elementary geometry to architectural description. A related adjective you may encounter is مثلثی (mosallasi), meaning “triangular in shape,” used to describe objects rather than the abstract shape itself.
How to use it
- سقف خانهشون شکل مثلث داره. (saqf-e khune-shun shakl-e mosallas dâre.) “The roof of their house has a triangular shape.”
- مثلث سه ضلع داره. (mosallas se zal’ dâre.) “A triangle has three sides.”
- معلم یک مثلث قرمز روی تخته کشید. (mo’allem yek mosallas ghermez ru-ye takhte keshid.) “The teacher drew a red triangle on the board.”
- این نشانه مثلثیه، یعنی خطر. (in neshune mosallasiye, ya’ni khatar.) “This sign is triangular, meaning danger.”
Cultural note
In Iranian Islamic geometry, triangular forms appear frequently as structural elements within larger star and polygon patterns on tilework and plasterwork. The word مثلث also appears in classical Persian poetry and music theory in the general sense of “threefold,” and its Arabic root makes it immediately recognizable across all Arabic-influenced languages of the region, which helped establish it as the shared scientific term throughout the Islamic scholarly tradition.