Scalpel and piston pump: what they have in common

1. Step 1. Scalpel — evolved from — Knife. A surgical knife.
2. Step 2. Knife — is part of — Overlocker. A knife for trimming the edge.
3. Step 3. Overlocker — has part — Needle. Needles sew the stitch.
4. Step 4. Needle — is part of — Syringe. A hollow needle.
5. Step 5. Syringe — works like — Piston pump. A syringe is a hand-operated piston pump.

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