I would like a definition of suhoor linguistically and legally [in Islamic law], if possible; many thanks to you.

Suhoor (with a dammah over the 's') refers to the act of partaking in the pre-dawn meal, i.e., eating and drinking at the time of sahur. Whereas sahur (with a fat-hah over the 's') refers to the food and drink itself that is consumed during that meal. It is a recommended and religiously encouraged act, based on the hadith: "Partake in the pre-dawn meal (sahur), for there is blessing in the pre-dawn meal (sahur)."