To reassemble something means to put it back together after taking it apart. When you disassemble a puzzle and then reassemble it, you're rebuilding it piece by piece until it's whole again. The prefix re- means “again,” so reassembling is assembling something for a second time.

People reassemble all kinds of things. A mechanic might disassemble an engine to fix a problem, then carefully reassemble all the parts in the correct order. If you take apart a LEGO creation to use the bricks for something new, you might later decide to reassemble the original design. When your family moves to a new house, movers might disassemble furniture to fit it through doorways, then reassemble it in your new rooms.

The word can also mean restoring something to its proper form and function. Successfully reassembling something requires remembering or understanding how the parts fit together. That's why instructions matter, and why smart builders take photos before disassembling complex things. When everything clicks back into place and works the way it should, you've reassembled it correctly.