Arooz shayari ke wazn ka classical ilm hai — wo ilm jo taweel aur qaseer hijaaon ki tarteeb ka mutaala karta hai, yaani wo aahang jo kisi sher ko mauzun banata hai. Yeh ilm aathvin sadi mein Arab lughwi Khalil ibn Ahmad al-Faraahidi ne Arabic shayari ke liye murattab kiya. Iranian shaaron ne ise apnaaya aur ismein tabdeeliyan keen; Urdu ne sattarween aur aThaarween sadi mein yeh nizaam Farsi se warse mein liya aur apni rivaayat banaai.
Urdu ka wazn kameeti (quantitative) hai — English ki tarah zor par mabni nahin. Ahem baat yeh hai ke har hijaa taweel hai ya qaseer. Taweel hijaa wo hai jismein sada ke baad saakin aaye, ya jis ka harf-e-illat taweel ho (alif, vaao, ye). Qaseer hijaa wo hai jismein ek harf ke saath mukhtasar sada ho. Bahr ka matlab hai taweel aur qaseer hijaaon ki ek mutayyan tarteeb. Kisi satar ko “falaan bahr mein” kehne ka matlab yeh hai ke us ki hijaayen — tarteeb se paRhi jaayein — us mutayyan namoone se bilkul milti hain.
Yeh tool wahi taqti chand seconds mein aap ke liye kar deta hai. Lekin yeh samajhna ke koi sher kyun asar karta hai, wo baat hai jo qaari ko shayar banaati hai.