piece
A single part of something larger or whole.
Piece is a single part of something, or one item from a larger group. When you eat a piece of cake, you're having just one serving from the whole cake. When you work on a jigsaw puzzle, each individual piece connects with others to form the complete picture.
The word appears everywhere in daily life. A chess set contains 32 pieces: pawns, rooks, knights, bishops, queens, and kings. A band might perform a musical piece they've been practicing. You might write a piece for the school newspaper, or tear a piece of paper from your notebook.
Piece often suggests something that belongs to a whole. If your bike falls apart, you'll need all the pieces to put it back together. When detectives investigate a mystery, they gather pieces of evidence until they solve the case. If you're learning something complicated, your teacher might explain it piece by piece, taking it one part at a time.
The phrase piece of cake means something is very easy (though no actual cake is involved). Piece of work describes someone difficult to deal with. And when friends argue, they might need to make peace, though that's spelled differently.