Dear Day, Teja was originally the Spanish tile, made out of clay, the rounded one. Nowadays you may also use the word "teja" for asphalt shingles. A Tejado would be used only for a roof made out of Spanish tiles. A techo would mean generally the roof, even those made out of Spanish tiles. We could say also "un techo de tejas" instead of "tejado", it depends on the country. In my country, the word "tejado" is not normally used, we use instead "techo". Saludos, Antonio

"If a roof has tiles it is a tejado. Otherwise it can just be called a techo" ... yes, it is right! (Un "techo" puede estar cubierto de "tejas").

"Techo" means roof.

Teja es una pieza de barro cocido, generalmente de forma acanalada, que, encajada con otras, forma parte de la cubierta de un tejado y sirve para que el agua de la lluvia pueda resbalar por ella. Muchas tejas =Tejado Techo=techado. Es la cubierta de un edificio o construcción, de tejas o láminas de zinc.