Insulin
Etymology
From Latin "insula" (island), because insulin is made in clusters of cells in the pancreas called the islets of Langerhans — literally little islands of tissue. The hormone is named for its birthplace, not its function.
noun · /IN-suh-lin/
A hormone that lets the body move sugar out of the blood and into cells for fuel.
What it names
Reach for it when you mean the key that unlocks cells to take in blood sugar — the hormone whose failure defines diabetes.
Example
Without enough insulin, sugar builds up in the blood instead of feeding the cells.
Related idea
Insulin lowers blood sugar; its counterpart glucagon raises it, the two forming a thermostat for fuel. In type 1 diabetes the body makes almost no insulin, while in type 2 the cells stop responding to it — same hormone, opposite failures.