An adjective meaning “sloping”, usually “sloping down” (PE17/24), with am(ba)penda being “uphill, ✱sloping up” (Ety/AM²). The adjective penda also has an implication of steeply sloping (PE17/173).
Conceptual Development: The word ᴱQ. penda first appeared in the Early Noldorin Dictionary as an element in ᴱQ. ambapenda “uphill”. Its Early Noldorin and Early Telerin cognates ᴱN. benn and ᴱT. benda were used for both sloping up and down hill, so the Early Qenya form was likely the same. The primitive form in this document was ᴱ✶bendā, with initial b- > p- as was the case in Early Qenya (later b- > v-).
In The Etymologies of the 1930s it first appeared as ᴹQ. nenda “sloping” derived from ᴹ√DEN “hillside, slope”, but the meaning of this root was change to ᴹ√DEN “hole; gap, passage” (Ety/DEN). Tolkien introduced a new root ᴹ√PEN(ED) with the derivative ᴹQ. penda “sloping down, inclined” (Ety/PEN), and this notion that penda was specifically for downwards slopes reappeared in later writings (PE17/24). In later writings, though, its root form was √PED instead of ᴹ√PEN, as √PEN was given the new sense “lack, be without” (PE17/173; WJ/375).
penda adj. "sloping down, inclined" (PEN/PÉNED), "steeply inclined, sloping down" (PE17:24)