noun
A piece of furniture for sitting or lying down, typically with a back and armrests, often found in living rooms.
新しい寝椅子をリビングに置いた。
I put a new sofa in the living room.
彼は寝椅子に横になって本を読んでいる。
He is lying on the couch reading a book.
長椅子 is a long bench or settee, often without a back or with a simple back, while 寝椅子 implies a more comfortable piece for lounging or sleeping.
Compound of 寝 (ne, 'sleep') + 椅子 (isu, 'chair'). The reading ねいす is a straightforward combination of the two components.