spiral ratchet screwdriver: a screwdriver with a ratchet (so the blade turns in only one direction) and a spiral in the handle (so the blade rotates) with downward pressure on the handle
screwdriver: a hand tool for driving screws; has a tip that fits into the head of a screw
ribosome: an organelle in the cytoplasm of a living cell; they attach to mRNA and move down it one codon at a time and then stop until tRNA brings the required amino acid; when it reaches a stop codon it falls apart and releases the completed protein molecule for use by the cell